by Stacey Chamberlain
Clinical Decision Rules (CDRs), also known as Decision “Instruments” or “Aids,” are evidence-based tools to assist the practitioner in decision-making for common complaints. In the Emergency Department (ED) setting, these decision aids are often used to help identify patients that might be higher risk for serious conditions such as pulmonary embolism (PE) or subarachnoid hemorrhage (SAH), or they are used to prevent overuse of unnecessary testing, which is how many of the orthopedic rules are applied.
CDRs, despite being called “Rules,” are not meant to replace critical thinking from experienced practitioners. In fact, many of the CDRs have been directly compared against clinician gestalt or clinical practice, and they do not always fare better. Additionally, some rules actually incorporate clinician gestalt whereas the rule cannot even be applied unless the pre-test probability (based on physician’s judgment of the likelihood of the disease) is below a pre-determined threshold. Also, for a CDR to be useful to a practitioner, it must be practical. If a CDR is developed that has too many complicated variables, it is unlikely to be applied in a busy clinical environment.
Another caveat to the application of CDRs is that they must be applied appropriately. CDRs evolve through a process of derivation to validation to impact analysis of the tool. After the tool is derived (level 4 evidence), the tool is validated in a limited patient setting (level 3 evidence), then a broader validation setting (level 2 evidence) and finally, the impact of the tool is assessed (level 1 evidence). These levels are important to caution the novice learner against applying every CDR derived and published automatically into their clinical practice. The tool must be validated in a patient population with similar characteristics to the practitioner’s patient population. For example, the tool may not perform the same (have the same sensitivity and specificity) if the prevalence of disease is different between the study and actual patient populations. Also, the practitioner must be familiar with the inclusion and exclusion criteria for a particular tool. If not, the tool could be misused. For example, if the tool was derived and validated for a patient population over the age of 18, it should not be inappropriately applied in a pediatric setting.
The practitioner must also understand the purpose of the CDR and whether it is a one-way or two-way rule. As noted by Green, for example, the Ottawa Ankle Rules are intended to be a two-way rule; if the patient meets criteria, you do an X-ray. If they don’t meet criteria, you do not do an X-ray. There are two paths you can take after you apply your CDR. Alternatively, the pulmonary embolism rule-out criteria (PERC) demonstrate a one-way rule. This tool was developed to identify a subset of patients at very low risk for PE such that no further testing need be done. If the patient is “PERC positive,” this should not imply that further testing for PE such as a D-dimer should be done. Whether or not additional testing should be done remains up to the practitioner and depends on many variables including whether an alternate diagnosis is much more likely. PERC was simply designed to help “rule out” the diagnosis of PE, not “rule in.” This rule only guides you down one path, potentially to do no testing; it makes no judgment as to what you should do if the patient is “PERC positive.”
In addition to CDRs, there are many risk stratification tools or scales that are currently used for serious conditions such as pulmonary embolism (PE) and acute coronary syndrome (ACS). Others are being developed for use in the ED setting for common conditions such as congestive heart failure (CHF), chronic obstructive pulmonary disease (COPD) and transient ischemic attack (TIA) to identify patients at higher risk for acute severe complications. From a practical perspective, the ED physician will often use these risk stratification devices to help determine which patients require admission. However, these tools are less prescriptive in that they are not rules that suggest what a practitioner should or should not do; rather, they help the physician more objectively look at the risk for an individual patient. Then the practitioner must decide what level of risk they are comfortable with in regards to inpatient or outpatient management, which may greatly depend on the resources available in those environments. Most of the risk stratification tools encompass multiple variables with more complicated scoring systems; as they are not easily memorized, most of these would typically be used by ED physicians with real-time access to a computer or smartphone with appropriate apps.
Given the many pitfalls noted above regarding CDRs, the goals of using evidence-based medicine to reduce practice variability, maximize use of resources, and help identify and diagnose high-risk conditions are important. It is equally important that the ED physician critically appraise these tools and selectively apply them in appropriate ways. The remainder of this chapter will use case scenarios to review the most commonly used CDRs in the ED setting.
The useful FOAM reference MDCalc.com provides a summary of the most common tools that are being used with easy-to-use online calculators, additional information on inclusion and exclusion criteria, and pearls and pitfalls for each tool.
A 28-year-old man presents to the ED with left ankle pain after twisting his ankle playing basketball. He is able to bear weight and notes pain and swelling to the lateral aspect of the ankle (he points to just below the lateral malleolus). He denies weakness, numbness, or tingling and has no other injuries. On exam, he is neurovascularly intact. Edema and tenderness are noted slightly anterior and inferior to the lateral malleolus. There is no point tenderness to the distal posterior malleoli bilaterally.
Should you get an X-ray to rule out fracture?
Ottawa Ankle Rule
- Pain in the malleolar zone and any one of the following:
- Bone tenderness along the distal 6 cm of the posterior edge or tip of the tibia (medial malleolus), OR
- Bone tenderness along the distal 6 cm of the posterior edge or tip of the fibula (lateral malleolus), OR
- An inability to bear weight both immediately after the trauma and in the ED for four steps.
Ottawa Foot Rule
- Pain in the midfoot zone and any one of the following:
- Bone tenderness at the base of the fifth metatarsal, OR
- Bone tenderness at the navicular bone, OR
- An inability to bear weight both immediately after the trauma and in the ED for four steps.
Ottawa Knee Rule
- Knee injury with any of the following:
- Age 55 years or older
- Tenderness at head of fibula
- Isolated tenderness of patella
- Inability to flex to 90°
- Inability to bear weight both immediately after the trauma and in the ED (4 steps)
Pittsburgh Knee Decision Rule
- Mechanism: blunt trauma or fall
- Age < 12 or > 50
- Unable to bear weight 4 steps in the ED
Some of the longest standing and most widely accepted CDRs are the Ottawa knee, ankle, and foot rules. These rules are to help practitioners identify patients with an extremely low risk of fracture such that X-rays do not need to be done, thus limiting the risks and costs of unnecessary testing. The sensitivity of these rules has been found to be 98.5-100%. In impact study of the Ottawa knee rule, application of the rule decreased the use of knee radiography without patient dissatisfaction or missed fractures and was associated with reduced waiting times and costs. These rules have been validated in pediatric populations as well with similar sensitivities (98.5-100%).
A less studied rule for knee trauma to determine the need for radiography is the Pittsburgh Decision Rule (PDR). It differs from the Ottawa rule in that it looks at the mechanism of injury and applies to a different age group; also, point tenderness is not used in the PDR. Its original derivation study found this rule to be 100% sensitive. Two studies compared the PDR and Ottawa knee rules and found the PDR to perform better with similar sensitivities but better specificity for the PDR (51-60% versus 27%). However, one validation study for the PDR found the sensitivity to be as low as 77%. Additionally, while the Ottawa rule has been validated in children as young as two years old, the PDR excludes children younger than 12.
Case 1 Discussion
In the above case, using either CDR, an X-ray is unnecessary.
A 57-year-old man fell from a height of 12 feet while on a ladder. He did not pass out; he reports that he simply lost his footing. He fell onto a grassy area, hitting his head and complains of neck pain. He did not lose consciousness and denied headache, blurry vision, vomiting, weakness, numbness or tingling in any extremities. He denies other injuries. He was able to get up and ambulate after the fall and came in by private vehicle. He has not had previous spine surgery and does not have known vertebral disease. On exam, he is neurologically intact with a GCS of 15, does not appear intoxicated and has moderate midline cervical spine tenderness.
Should you get imaging to rule out a cervical spine fracture?
Canadian C-spine Rule
- Age ≥ 65
- Extremity paresthesias
- Dangerous mechanism (fall from ≥ 3ft / 5 stairs, axial load injury, high-speed MVC/rollover/ejection, bicycle collision, motorized recreational vehicle)
NEXUS Criteria for C-spine Imaging
- Focal neurologic deficit present
- Midline spinal tenderness present
- Altered level of consciousness present
- Intoxication present
- Distracting injury present
Both the Canadian C-spine Rule (CCR) and NEXUS Criteria are widely employed in clinical practice to reduce unnecessary cervical spine imaging in trauma patients with neck pain or obtunded trauma patients. The CCR uses mechanism and age criteria, whereas the NEXUS Criteria incorporates criteria including midline tenderness and additional factors that might limit a practitioner’s exam. The CCR can be difficult for some practitioners to remember all the criteria that qualify as a dangerous mechanism and is limited to ages > 16 and < 65. However, it can be used in intoxicated patients if the patients are alert and cooperative, allowing a full neurologic exam. The NEXUS Criteria are applicable over any age range (> 1 year old), but the sensitivity may be low in patients > 65 years of age. A single comparison study found the CCR to have better sensitivity (99.4% versus 90.7%); however, the study was performed by hospitals involved in the initial CCR validation study.
Case 2 Discussion
By applying either criteria to this case, the patient would require C-spine imaging as by CCR, the patient would meet criteria for dangerous mechanism, and by NEXUS, the patient has midline tenderness to palpation.
A 36-year-old woman slipped on ice and fell and hit her head. She reports loss of consciousness for a minute after the event, witnessed by a bystander. She denies headache. She denies weakness, numbness or tingling in her extremities and no changes in vision or speech. She has not vomited. She remembers the event except for the transient loss of consciousness. She doesn’t use any blood thinners. On physical exam, she has a GCS of 15, no palpable skull fracture and no signs of a basilar skull fracture.
Should you get a CT head for this patient to rule out a clinically significant brain injury?
Canadian CT Head Rule
- High-Risk Criteria (rules out the need for neurosurgical intervention)
- GCS < 15 at two hours post-injury
- Suspected open or depressed skull fracture
- Any sign of basilar skull fracture (hemotympanum, Raccoon eyes, Battle’s sign, CSF oto or rhinorrhea)
- Medium Risk Criteria (rules out clinically important brain injury)
- Retrograde amnesia to event ≥ 30 minutes
- Dangerous mechanism (pedestrian struck by motor vehicle, ejection from the motor vehicle, fall from > 3 feet or > 5 stairs)
The Canadian CT Head Rule (CCHR) only applies to patients with an initial GCS of 13-15, witnessed loss of consciousness (LOC), amnesia to the head injury event, or confusion. The study was only for patients > 16 years of age. Patients were excluded from the study if they had “minor head injuries” that didn’t even meet these criteria. Patients were also excluded if they had signs or symptoms of moderate or severe head injury including GCS < 13, post-traumatic seizure, focal neurologic deficits, or coagulopathy. Other studies have looked at different CDRs for traumatic brain injury including the New Orleans Criteria (NOC). However, CCHR has been found to have superior sensitivity and specificity.
Case 3 Discussion
By applying this rule to the above case, the patient should be considered for imaging due to the mechanism. A fall from standing for an adult patient would constitute a fall from > 3 feet; therefore, although the patient would not likely be high risk and need neurosurgical intervention, the patient might have a positive finding on CT that in many practice settings would warrant an observation admission.
A 20-month-old female was going up some wooden stairs, slipped, fell down four stairs, and hit the back of her head on the wooden landing at the bottom of the stairs. She did not lose consciousness and cried immediately. She was consolable after a couple of minutes and is acting normal per her parents. She has not vomited. On exam, she is well-appearing, alert, and has a normal neurologic exam. She is noted to have a left parietal hematoma measuring approximately 4×4 cm.
Should you get CT imaging of this child to rule out clinically significant head injury?
PECARN Pediatric Head Trauma Algorithm
- Age < 2
- GCS < 15, palpable skull fracture, or signs of altered mental status
- Occipital, parietal or temporal scalp hematoma; History of LOC≥5 sec; Not acting normally per parent or Severe Mechanism of Injury?
- Age ≥ 2
- GCS < 15, palpable skull fracture, or signs of altered mental status
- History of LOC or history of vomiting or Severe headache or Severe Mechanism of Injury?
The PECARN (Pediatric Emergency Care Applied Research Network) Pediatric Head Trauma Algorithm was developed as a CDR to minimize unnecessary radiation exposure to young children. The estimated risk of lethal malignancy from a single head CT in a 1-year-old is 1 in 1000-1500 and decreases to 1 in 5000 in a 10-year-old. Due to these risks, in addition to costs, length of stay and potential risks of procedural sedation, this CDR is widely employed given the frequency of pediatric head trauma ED visits. This CDR has the practitioner use a prediction tree to determine risk, but unlike some other risk stratification tools, the PECARN group does make recommendations based on what they consider acceptable levels of risk. In the less than 2-year-old group, the rule was found to be 100% sensitive with sensitivities ranging from 96.8%-100% sensitive in the greater than two-year-old group.
This algorithm does have some complexity and ambiguity. It requires the practitioner to know what were considered signs of altered mental status and what were considered severe mechanisms of injury. In addition, certain paths of the decision tree lead to intermediate risk zones. In these cases, the recommendation is “observation versus CT,” allowing for the ED physician to base his/her decision to image or not based on numerous contributory factors including physician experience, multiple versus isolated findings, and parental preference, among others.
Other pediatric head trauma CDRs rules have been derived and validated; however, in comparison trials, PECARN performed better than the other CDRs.1 Of note, in this study, physician practice (without the use of a specific CDR) performed as well as PECARN with only slightly lower specificity.
Case 4 Discussion
For purposes of the case study, the patient falls into an intermediate risk zone of clinically important brain injury. However, a sub-analysis of patients less than two years old with isolated scalp hematomas suggests that patients were higher risk if they were < 3 months of age, had non-frontal scalp hematomas, large scalp hematomas (> 3cm), and severe mechanism of injury. Given the large hematoma in the case study patient and a severe mechanism of injury (a fall of > 3 feet in the under two age group), one might more strongly consider imaging due to these two additional higher risk factors.
PECARN Abdominal Trauma
- Evidence of abdominal wall trauma/seatbelt sign or GCS < 14 with blunt abdominal trauma (if no, go to next point)
- 5.4% risk of needing intra-abdominal injury intervention
- Abdominal tenderness (if no, go to next point)
- 1.4 % risk of intra-abdominal injury intervention
- Thoracic wall trauma, complaints of abdominal pain, decreased breath sounds, vomiting
- 0.7% risk of intra-abdominal injury intervention
A CDR for pediatric blunt abdominal trauma has been derived by the PECARN group but not yet validated. This CDR uses a seven-point decision rule. If the patient does not have any of these findings, the patient would be considered “very low risk” with a 0.1% risk of intra-abdominal injury intervention required. A study did compare the PECARN CDR versus clinical suspicion and found that the CDR had significantly higher sensitivity (97.0% vs. 82.8%) but lower specificity (42.5% vs. 78.7%). However, abdominal CTs were done in 33% of patients with clinical suspicion < 1%, meaning that even though clinical suspicion had higher specificity, this often did not translate into clinical practice. Validation of the PECARN rule has the potential to therefore improve both sensitivity and specificity compared to physician practice, but this remains to be seen.
A 24-year-old woman presents with headache that began three hours prior to arrival to the ED. The patient was at rest when the headache began. The headache was not described as “thunderclap,” but it did reach maximum severity within the first 30 minutes. The headache is generalized and rated 10/10. She denies head trauma, weakness, numbness, and tingling in her extremities. She denies visual changes, changes in speech and neck pain. She has not taken anything for the headache. She does not have a family history of cerebral aneurysms or polycystic kidney disease. On physical exam, she has a normal neurologic exam and normal neck flexion.
Should you do a head CT and/or a lumbar puncture to evaluate for a sub-arachnoid hemorrhage in this patient?
Ottawa SAH Rule
- Investigate if ≥1 high-risk variables present:
- Age ≥ 40
- Neck pain or stiffness
- Witnessed loss of consciousness
- Onset during exertion
- Thunderclap headache (instantly peaking pain)
- Limited neck flexion on exam
A CDR to determine risk for sub-arachnoid hemorrhage (SAH) was derived and has been externally validated in a single study. The CDR’s purpose was to identify those at high risk for SAH and included those with acute non-traumatic headaches that reached maximal intensity within one hour and who had normal neurologic exams. Of note, the rule has many inclusion and exclusion criteria that the ED physician must be familiar with and was only derived for patients 16 years or older. The study authors note that the CDR is to identify patients with SAH; it is not an acute headache rule. In the validation study, of over 5,000 ED visits with acute headache, only 9% of those met inclusion criteria. Also, clinical gestalt again plays a role as the authors suggest not to apply the CDR to those who are ultra-high risk with a pre-test probability for SAH of > 50%.
The Ottawa SAH Rule was 100% sensitive but did not lead to reduction of testing vs. current practice. The authors state that the value of the Ottawa SAH Rule would be to standardize physician practice in order to avoid the relatively high rate of missed sub-arachnoid hemorrhages.
Case 5 Discussion
By applying the Ottawa SAH Rule, this patient is low risk and does not require further investigation for a SAH.
A 19-year-old female presents with sharp right flank pain and shortness of breath that started suddenly the day prior to arrival. The pain is worse with deep inspiration but not related to exertion and not relieved with ibuprofen. She denies anterior chest pain, cough, and fever. She denies leg pain or swelling and recent travel, immobilization, trauma, or surgery. She has no anterior abdominal pain, no dysuria or hematuria and no personal or family history of gallstones, kidney stones, or blood clots. She’s never had this pain before, has no significant past medical history and her only medication is birth control pills. On exam, her vital signs are within normal range, she has normal cardiac and pulmonary exams, no costovertebral angle tenderness, no chest wall or abdominal tenderness and no leg swelling.
Do you need to do any studies to evaluate this patient for a pulmonary embolism?
Pulmonary Embolism Rule-Out Criteria (PERC)
- Age ≥ 50
- Heart rate ≥ 100
- O2 sat on room air < 95%
- Prior history of venous thromboembolism
- Trauma or surgery within 4 weeks
- Exogenous estrogen
- Unilateral leg swelling
The PERC CDR was originally derived and validated in 2004 and with a subsequent multi-study center validation in 2008. In the larger validation study, the rule was only to be applied in those patients with a pre-test probability of < 15%, therefore incorporating clinical gestalt prior to using the rule. PERC is a one-way rule, as mentioned above, which tried to identify patients who are so low-risk for pulmonary embolism (PE) as to not require any testing. It does not imply that testing should be done for patients who do not meet criteria, and it is not meant for risk stratification, as opposed to the Wells’ and Geneva scores.
Case 6 Discussion
In order to apply the PERC CDR to the case study patient, the ED physician pre-supposes a pre-test probability of < 15%. If the ED physician has a higher pre-test probability than that, he/she should not use the PERC CDR. If the ED physician, in this case, did indeed have a pre-test probability of < 15%, the case study patient would fail the rule-out due to her use of oral contraceptives. In that case, the ED physician would need to determine if he/she would do further testing which could include a D-dimer, CT chest with contrast, ventilation/perfusion scan, or lower extremity Doppler studies to evaluate for deep vein thromboses (DVTs). The PERC CDR gives no guidance in this case.
Risk Stratification Tools
A 68-year-old male presents with acute onset of shortness of breath and right-sided sharp chest pain, worse with deep breathing. He denies chest pain with exertion, no cough, fever or hemoptysis, no leg pain or swelling, no recent travel, surgery or immobilization. He has a history of prostate cancer and completed his treatment with radiation therapy four months ago. On exam, his heart rate is 90, O2 saturation is 98% with a normal respiratory rate, blood pressure, and temperature. His cardiac and pulmonary exams are normal, and there is no calf tenderness or swelling.
How should you proceed with this patient’s work up for PE?
Wells and Revised Geneva Score for Pulmonary Embolism (PE)
Wells’ Criteria for Pulmonary Embolism
|Clinical signs and symptoms of DVT||+3|
|PE is #1 diagnosis, or equally likely||+3|
|Heart rate > 100||+1.5|
|Immobilization at least 3 days, or Surgery in the Previous 4 weeks||+1.5|
|Previous, objectively diagnosed PE or DVT||+1.5|
|Malignancy w/ Treatment within 6 mo, or palliative||+1|
Score >4 = High probability
Score 2–4 = Moderate probability
Score <2 = Low probability
Geneva Score (Revised) for Pulmonary Embolism
|Risk factors||Age > 65||+1|
|Previous DVT or PE||+3|
|Surgery (under general anesthesia) or lower limb fracture in past 1 month||+2|
|Active malignant condition||+2|
|Symptoms||Unilateral lower limb pain||+3|
|Signs||Heart rate < 75||0|
|Heart rate 75 - 94||+3|
|Heart rate ≥ 95||+5|
|Pain on lower limb deep venous palpation and unilateral edema||+4|
The Wells’ Criteria for PE is a risk stratification score with different point values assigned to different criterion. Its purpose is to identify patients who have a lower risk for PE in order to potentially avoid unnecessary testing and the risks and costs associated with it. The criteria have been validated in the ED setting. In the initial three-tier model, a patient with 0-1 points was considered to be in a low-risk group (1.3% prevalence of PE in an ED population) versus patients with a moderate score of 1-6 ( 16.2% prevalence), and those with a high score of >6 ( 37.5% prevalence). Subsequent studies have been done to apply a simplified version of the Wells’ Criteria and also to use the Wells’ Criteria along with D-dimer testing in a dichotomous manner (two-tier model) where a score of 4 or less (“PE Unlikely” group) combined with a negative D-dimer would achieve sufficiently low probability of PE so as not to pursue further workup. This two-tier model is supported by the American College of Physicians (ACEP) Clinical Guidelines. A two-tier model using a cut-off of less than 6 for low risk was studied in pregnant patients with a negative predictive value of 100%.
The original Geneva score included the use of chest radiography and an ABG, whereas the revised score (rGeneva) uses only clinical criteria. A patient with a rGeneva score of 0-3 is considered the low risk with a < 10% prevalence of PE. A score of 4-10 identifies intermediate-risk patients, and a score of 11+ is high risk (>60% prevalence or PE).
The Wells and rGeneva scores have been compared and found to have overall similar accuracy. These PE risk stratification tools are meant to be applied in those patients with concern for PE as a diagnosis. If PE is not under consideration, the tools should not be applied. Practically speaking, for many ED physicians, these tools are used to help risk stratify patients to identify those who are very low-risk such that no testing should be done, low to intermediate risk such that D-dimer testing would be a useful diagnostic tool, or high risk such that even if a D-dimer were negative, the post-test probability would remain high enough that further testing should be pursued. One recent study found that physician gestalt actually performed better than either the Wells or rGeneva scores. However, guidelines from the Clinical Practice Committee of the American College of Physicians (ACP) were published in 2015 that outline best practice advice including advocating that clinicians should use validated CPRs to estimate pre-test probability in patients in whom acute PE is being considered.
Case 7 Discussion
This patient’s Wells’ score is 4. Although subject to ED physician judgment, PE could be considered at least equally as likely as any other diagnosis given the absence of other findings to explain his shortness of breath (no crackles or wheezing on exam, no cough or fever). The patient’s rGeneva score is 6. An “active malignant condition” is defined as a “solid or hematologic malignant condition, currently active or considered cured < 1 year.” Using the dichotomous Wells’ approach, the patient would be considered “PE Unlikely;” using the rGeneva, the patient would be intermediate risk. The ACP Guidelines would suggest that a D-dimer should be done in this patient, adjusted for age, to determine the need for possible imaging to evaluate for PE.
A 50-year-old male presents to the ED complaining of chest pain for two days. His pain is substernal, non-radiating, described as a tightness, not related to exertion. He has no associated shortness of breath, nausea or diaphoresis. No cough or fever. He’s never had this pain before. He has a history of hypertension but no other cardiac risk factors. His exam in the ED is normal, and his EKG and initial troponin are normal.
Does this patient require additional cardiac workup in the ED or admission to hospital for additional workup? Can this patient be safely discharged for outpatient follow-up?
HEART Score for Cardiac Events
|EKG||Significant ST depression||+2|
|Non specific repolarization disturbance||+1|
|Risk Factors (include: hypercholesterolemia, hypertension, diabetes mellitus, cigarette smoking, positive family history, obesity)||≥ 3 risk factors or history of atherosclerotic disease||+2|
|1-2 risk factors||+1|
|No risk factors known||0|
|Troponin||≥ 3× normal limit||+2|
|1-3× normal limit||+1|
|≤ normal limit||0|
The HEART Score is used to risk stratify chest pain patients in the ED to identify those at risk for major adverse cardiac events (MACE) within six weeks. With the HEART Score, low-risk patients have a score of 0-3 and have a less than 2% risk of MACE at 6 weeks. The HEART Score differs from the Thrombolysis in Myocardial Infarction (TIMI), and Global Registry of Acute Coronary Events (GRACE) scores as those scores measure the risk of death for patients with diagnosed acute coronary syndromes (ACS) rather than identifying patients who have cardiac-related chest pain in the first place. Additionally, even with low TIMI scores for those diagnosed with ACS in the ED, there is still a 4.7% risk of a bad outcome. This may be of little utility to the ED physician who finds this risk level unacceptable.
Case 8 Discussion
This patient’s HEART Score is 3 if the physician considers the history “moderately suspicious.” The patient is at low risk for a major cardiac event in the next six weeks so that the ED physician could consider outpatient follow-up. Again, however, the risk stratification scores are not prescriptive, however. Decision-making must be done by the clinician based on his/her judgment, resources available, and comfort with certain levels of risk.
A four-year-old boy presents to the ED with a complaint of sore throat for one day associated with cough and fever. On exam, he is febrile to 38.5 degrees Celsius, has bilateral tonsillar exudates, and anterior cervical lymphadenopathy.
How should you proceed with the workup for this child for possible strep? Options include treating empirically, doing a rapid point-of-care strep test, sending a throat culture, or supportive treatment.
Centor Score (Modified) for Streptococcal Pharyngitis
|45 or older||-1|
|Exudate or swelling on tonsils||+1|
|Tender/swollen anterior cervical lymph nodes||+1|
|Fever (T > 38°C, 100.4°F)||+1|
The Centor Score is a risk stratification tool to look at clinical criteria that suggest a greater likelihood of strep pharyngitis that may prompt the ED physician to prescribe antibiotics. It was originally designed for use in adults, but a modified score has been validated for use in children > 2 years of age and adults that includes age criteria as strep pharyngitis is a more common condition in children. In the absence of any of the criteria at any age group, the risk of strep is less than 10% (< 2.5% if 15 or older) and further testing is not necessary. With a score of 4 or more points, the probability of strep is greater than 50%, and some would advocate for empiric antibiotics in this group. However, as a risk stratification tool, ED physicians can adjust their practice according to their interpretation of the risks.
Antibiotics have been shown to reduce suppurative (peritonsillar abscess, cervical lymphadenitis, and mastoiditis) and non-suppurative (e.g., acute rheumatic fever) complications of strep pharyngitis and shorten the duration of clinical symptoms as well as reducing transmission. Rapid antigen detection tests have been found to have a sensitivity between 70 and 90% and a specificity of ≥95%. Some authors recommend rapid antigen detection testing (RADT) only for children with high clinical scores (using Centor or other published clinical criteria) or if the results of the standard throat culture will not be available for more than 48 hours. Additionally, the presence of particular clinical criteria may impact the ED physician’s decision to test and/or treat. Studies looking at different clinical prediction scores (including Centor) found that the presence of tonsillar exudates conferred the highest odds of having streptococcus infection.
Case 9 Discussion
The patient has a Centor Score of 4. Some clinicians would use this high-risk clinical score to justify further testing with an RADT or a throat culture. Others would treat empirically, especially given the presence of exudates which has a higher specificity than some of the other clinical findings. This decision may be based on additional factors such availability and processing times of diagnostic testing and ease of patient follow-up.
A 30-year-old male presents to the ED with nausea, vomiting, and epigastric discomfort for one day. He vomited multiple times, initially non-bloody, then developed some blood in the vomit during the last two episodes, which he quantified as a teaspoon in each. He denies melena or hematochezia. He has no diarrhea, fever, or syncope. He denies a history of liver or heart problems. On exam, he has normal vital signs with an initial blood pressure of 128/78 in the ED, and his abdomen is non-tender. His hemoglobin is 13.5, and BUN is 5.
Does this patient need admission for further monitoring or evaluation of his upper GI bleed?
Glasgow-Blatchford Risk Score
|BUN in mg/dL|
|18.2 to 22.4||2|
|22.5 to 28||3|
|28.1 to 70||4|
|70.1 or greater||6|
|Hemoglobin, men g/dL|
|12 to 13||1|
|10 to 11.9||3|
|9.9 or less||6|
|Hemoglobin, women g/dL|
|10 to 12||1|
|9.9 or less||6|
|Systolic Blood Pressure, mmHg|
|Heartrate >100 peats per minute||1|
The Glasgow-Blatchford Bleeding Score (GBS) uses clinical information as well as some diagnostic testing to risk stratify upper GI bleeding patients. It should not be used for lower GI bleeding patients or patients in whom the source of GI bleeding is unclear. A score of 0 is considered low risk. Any score higher than 0 is high risk for needing a medical intervention of transfusion, endoscopy, or surgery; therefore, the presence of any of the above criteria would be considered high risk. The tool assigns different point values to different gradations of the variables present to a possible highest possible score of 29.
Case 10 Discussion
The patient does not meet any of the criteria in the GBS and would be considered low risk. The patient does not demonstrate any signs of lower GI bleeding and could likely be safely discharged home based on this risk stratification.
A 45-year-old woman presents with syncope immediately prior to arrival. She was feeling generalized fatigue prior to the syncopal episode. She denies chest pain, palpitations, or shortness of breath. She has not had vomiting or diarrhea. She has been taking PO today but has a decreased appetite. She has no known medical problems. On exam, her initial BP is 86/48 which improves to 98/50 with 1L IVF. Her hematocrit is 31%, and her EKG and telemetry monitoring in the ED are normal.
Is this patient low risk for safe discharge home?
San Francisco Syncope Rule
- Congestive heart failure history
- Hematocrit < 30%
- EKG abnormal (new EKG change from any source, any non-sinus rhythm on
- EKG or monitoring)
- Shortness of breath symptoms
- Systolic BP < 90 mmHg at triage
The San Francisco Syncope Rule was derived in 2004. In its initial derivation and validation studies, it was found to have 92% and 98% sensitivity, respectively. Its use has become controversial, however, due to inconsistent validation studies where it has not performed as well. A systematic review of the literature from 2011 suggested that “the probability of a serious outcome given a negative score with the San Francisco Syncope Rule was 5% or lower, and the probability was 2% or lower when the rule was applied only to patients for whom no cause of syncope was identified after initial evaluation in the emergency department.” However, a meta-analysis from 2013 suggests that it only had 87% sensitivity for serious outcomes according to pooled results and that there was a broad range of false-negative rates among the included studies (range 0% to 48%). Although there is clearly no consensus on use of this tool to safely discharge patients with syncope home, if they do not meet these criteria, patients who do have criteria would be considered higher risk, possibly warranting observation, admission and/or further diagnostic studies.
Case 11 Discussion
Although the San Francisco Syncope Rule has failed to be consistently validated for use in identifying all high-risk patients, this patient fails the rule due to her initial SBP being less than 90. Therefore, this patient would, in any case, not be considered low-risk, and the ED physician might consider additional monitoring and/or evaluation.
Ottawa Heart Failure Risk Score, COPD Risk Scale and Canadian TIA Risk Score
These risk stratification tools are mentioned as they have all completed derivation studies and are in various stages of validation studies. The intent of these tools is to help the clinician develop risk estimates of short-term serious adverse events in ED patients. Although not yet ready for widespread usage, the ED physician should be aware of these. Additional studies need to be completed and published to determine the validity and impact of these scores, but they certainly have the potential to be useful adjuncts for the management of ED patients with these common conditions.
Refernces and Further Reading
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Links To More Information
- MDCalc.com. As noted in the chapter, MDCalc.com provides a summary of the most common tools that are being used with easy-to-use online calculators and additional information on inclusion and exclusion criteria and pearls and pitfalls for each tool.
- Those listed in this chapter are listed with links below:
- Ottawa Ankle Rule
- Pittsburgh Knee Decision Rule
- Canadian C-Spine Rule
- NEXUS Criteria for C-Spine Imaging
- Canadian CT Head Injury/Trauma Rule
- PECARN Pediatric Head Trauma Algorithm
- Pulmonary Embolism Rule-Out Criteria (PERC)
- Wells’ Criteria for PE
- Revised Geneva Score for PE
- HEART Score for Major Cardiac Events
- Modified Centor Score for Strep Pharyngitis
- Glasgow-Blatchford Bleeding Score
- San Francisco Syncope Rule
- Ottawa Ankle Rule
- Additional audio resources:
- Emergency Medicine Cases podcast: Clinical Decision Rules and Risk Scales. This hour-long podcast discusses the overall use of CDRs and Risk Scales and how they are developed and used, with a discussion with Dr. Ian Stiell, the “father of clinical decision rules” from Ottawa, Canada. http://emergencymedicinecases.com/episode-56-stiell-sessions-clinical-decision-rules-risk-scales/
- Agile MD app. You can download the AgileMD app for free and then download the EM Cases Summaries for free. Within EM Cases Summaries is a link to the “Ottawa CDRs and Risk Scales.” This includes shortcut to the Ottawa Ankle and Knee Rules, the Canadian C-spine and CT Head Rules, and the Ottawa COPD, Heart Failure, and TIA Risk Scores (as discussed in the above podcast).
- EMCrit podcast: Cervical Spine Injuries in the ED. Dr. Scott Weingart discusses these two CDRs and suggests an algorithm to use both in sequence. http://emcrit.org/podcasts/cervical-spine-injuries-i/