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Even though many are named “RULES”, they should not be.  Instead they should be considered TOOLS, CRITERIA, SCORES or perhaps GUIDELINES. 

The goal is to decrease imaging and thereby radiation and improve ED throughput.  A head to toe run of my most frequently used decision tools and scores are listed below.

IMPORTANT: you should know the exclusion criteria for each study.  Some of these decision tools have additional blind spots.

Shared Decision Making: To minimize risk of patient complaints and other “complications”, when not imaging, it may be useful to discuss the small remaining risk (usually 1-2%) with patient, chance they may need to return if worse or not better, and to document shared decision making.  If you want to copy our shared decision making template click here



Included: n = 42,412, age <18, GCS =15 (~5% +CT, ~1% ciTBI and ~1/1000 need surgery)

Excluded>24h, ground level fall, walking into object, prior CNS disease, penetrating injury

Abbreviations: ciTBI = clinically important Traumatic Brain Injury, PECARN = Pediatric Emergency Care Applied Research Network

Criteria: See below

Branch 1: AMS, abnormal neuro exam of e/o skull fracture on exam: risk of ciTBI >4% so CT all

Branch 2:  Risk of ciTBI ~1% if any of below factors present: CT or close observation w/o CT

  • Age <2y:   AMS, risky/unknown mechanism*, LOC >5sec, palpable fx, non-frontal hematoma, vomit
  • Age >2y:   AMS, risky mechanism*, any LOC, signs of basilar skull fx, vomiting, severe HA

If Branch 2 positive then decision whether or not to CT should be based on: # of factors present, worsening or not, provider experience & parent preference.  Isolated LOC <1 minute, isolated nonprogressive HA or isolated vomiting entails a risk <1%.  If multiple branch 2 red flags present then the risk is >1% risk so should order CT

* Risky Mechanism: Fall >5 stairs or >5ft, or if age <2y >3ft (height of sink/counter but not bed/table), Head struck by projectile or high-impact object, bad MVA, skating/scooter/bike w/o helmet

Benefit: decreases CT’s by 20-25%.  Cancer risk of CT ~1/5,000.

Validated: YES



Included: N =13,728 with head injury

Excluded: delay to care >24 hours

Abbreviations: NEXUS = National Emergency X-radiography Utilization Study

Criteria/MnemonicBEAN BASHBlood thinner, Emesis, Age >65, Neuro or Behavior abnl, AMS, Skull fx, Hematoma

Sensitivity: 98.3% for significant injury (not + CT).

Benefit: 13% for all 8 criteria plus exclusion criteria

Conclusion: Can’t construct a rule that is any better than clinical judgement




Included: N = 3121.

Excluded: Age <16, delay to care >24 hours, blood thinners, seizure

5 High risk criteria: GCS<15 @ 2h, sign of skull fx, vomiting >1, age >65y

2 Additional criteria: amnesia >30m, bad mechanism

Sensitivity: 100% (92-100%) for intervention using top 5, 98% for abnormal CT using all 7

Benefit: Scans reduced by 32% if all 7 criteria, and by 54% if only the 5 high risk criteria



HEAD: Merit based Incentive Payment System (MIPS)

Caveats: Not a study, but a CMS policy so should be defensible 

Policy: If head CT for trauma ordered, then document a reason below

Age >18:  1 of: severe HA, emesis, mechanism, thin blood, focal deficit, e/o skull fx, age >65

Age <18:  If head CT ordered document: “Patient NOT low risk according to PECARN criteria”


  • Headache that is severe/worsening
  • Emesis (even once)
  • Mechanism (see PECARN for concerning mechanisms)
  • Amnesia/KO >1 minute
  • Thin blood: Plavix, etc. riskier for acute bleed but less risky for delayed bleed than blood thinners
  • Observed & worse (We apply to ED obs or presentation beyond 24 hours)
  • Memory: if they don’t get 3/3 at 5 minutes, 2 tries allowed
  • Age >65
  • AMS
  • Skull fracture clinically: step-off or basilar




Included: 834,069 patients.  818 fractures

Excluded: Age <2, direct blow or penetrating injury, severe osteoporosis, cancer, severe arthritis

Abbreviations: NEXUS = National Emergency X-radiography Utilization Study

Criteria:  No intoxication, no distracting injury, A+Ox4, no neuro deficit, no midline spinal tenderness

Sensitivity:  99% sensitive for any neck fracture, 99.6% sensitive for clinically significant fracture

Caveats: Few patients age <8 in study

Benefit: If all criteria below satisfied then no imaging.  # of x-rays reduced by 33%

Other: No distracting injury was not defined.  The way I do it is to ask the patient something like, “when you are not moving anything do you have any pain that you feel is strong enough to distract you from noticing another injury?”




Included8924 patients. 151 fractures

Excluded: AMS, age <16, pregnant, paralysis, penetrating injury, repeat visit, prior neck disease

Exclusion: AMS/intoxication, age <16, pregnant, paralysis, penetrating injury, repeat visit.

Low Risk:  Simple rear-end MVA or ambulatory or delayed onset of pain or no midline tenderness

High Risk: Age >65, paresthesia, bad mechanism: fall >3ft, axial load, bad MVA, bike/ATV, rollover…

Application: If any low risk & no high risk criteria & can rotate 45° left & right then no x-ray

Sensitivity:  100% (98-100%) sensitive for clinically significant fracture.

Benefit: # of x-rays reduced by 42% if criteria plus exclusion criteria satisfied



Included: 8138 patients with chief complaint of dyspnea or chest pain

Excluded: Cancer, Beta-blocker use, medium or high clinical suspicion of PE

Abbreviations: PERC (PE Rule-out Criteria)

Criteria/Mnemonic: Vital signs & ABCDEFGH:

  • Pulse <100, SaO2 >94%
  • Age <50
  • no Beta blockers
  • no Cancer
  • no DVT or PE history
  • no Estrogen use
  • past Four weeks – no immobilization
  • no Gam (leg) swelling that is unilateral
  • no Hemoptysis

Sensitivity: 98%

Benefit: No need for D-Dimer or advanced imaging in 22%

Blind Spots: Active cancer, use of medications that lower the heart rate, medium or high clinical suspicion of PE



Included: 346 patients to determine when can use a higher D-dimer cutoff (double usual one)


  • Age < 18y
  • Blood thinner use

Abbreviations: YEARS

Criteria/Mnemonic: HAD

  • No clinical signs of DVT
  • No better Alternate diagnosis
  • No Hemoptysis

Sensitivity: ~99%

Benefit: Using a D-dimer cutoff of 1000 (twice usual cutoff) led to 14% fewer chest CT”s.

Validated: yes

Blind Spots:

More info

Lancet. 2017; 390:289-297



Included:  N = 122 in the 2008 Netherlands derivation study:

Excluded: No pain, STEMI (all other ED chest pain patients were included)

Criteria/Mnemonic: HEART:

Sensitivity: 97.5% but better in validation studies.  (see Validated section below)

Benefit: ~20% of ED chest pain patients can be sent home.  No need for admission or urgent advanced cardiac imaging if Score < 3

Blind Spots:

  1. If the chest pain has resolved and lasted <30 minutes then the EKG, troponin and repeat troponin may all be completely useless.  In such cases I would consider doubling the points for history.  If it is highly suspicious, give four points and if moderately suspicious give 2 points   
  2. If the AVERAGE risk for all comers in the low risk group (scores of 0-3) is in the 1% range after a repeat troponin, and those with scores of 2 or 3 have a higher risk than those with scores of 0 or 1, then it follows that those with a score of 0 or 1 likely have a risk <1%, but those with a score of 2 or 3 likely have a risk >1%.

Validated: YES, by multiple studies:

  • N = 303, MACE = 1% in low risk
  • N = 2440. MACE = 1.7% in low risk group:
  • N =1070. MACE = 0% if low risk and repeat troponin at 3 h negative, but confidence interval 72-100%
  • N = 1107, MACE = 1% if low risk and repeat troponin at 3 h negative



CHEST: Canadial Syncope Risk Score of 2016:

Included: 4030 pts, <24h since syncope, no obvious reason to admit, admitted or discharged

Excluded: LOC >5min, AMS after awake, witnessed seizure, major trauma, intoxication, language barrier, knocked out

Outcomes: 9.5% admitted, 3.6% adverse event rate (7-23% in prior studies, 0.2% were PE)

Criteria/Mnemonic: ABCD-TV: Axis, BP, Cardiac, Durations, Troponin, Vasovagal

  1. Prone to Vasovagal syncope
  2. No known prior Cardiac disease
  3. No SBP >180 or <90 while in ED
  4. Normal Troponin
  5. Normal QRS Axis (-30 to 110)
  6. QRS Duration <130ms
  7. QTc Duration <480ms
  8. No Cardiac syncope ED diagnosis
  9. Vasovagal ED diagnosis


  • 99.6% if likely vasovagal, unlikely cardiac & none of the 9 criteria
  • 99.2% if likely vasovagal, unlikely cardiac & only 1 of the 9 criteria
  • 97.7% if likely vasovagal, unlikely cardiac & only 2 of the 9 criteria

Benefitfewer admissions

Blind Spots: excluded patients, other EKG abnormalities, obvious indication for admission

Validated: Not as off 2020



Included: 1,048 patients from the CURB-65 international derivation study

Excluded: none found so far


  • Confusion
  • BUN >20
  • RR >30
  • BP <90/60
  • 65 or older
  • Lactate >2


Benefit: consider outpatient for score 0-1 as 30 day mortality <2%.  I don’t trust this 

Blind Spots: Very unlikely that I would send home a patient with pneumonia and new confusion, RR >30, BP <90/60 or lactae >2.  Also very unlikely I would be particularly worried if a patient’s BUN was >20 or their age >65 if they otherwise looked good.

Validated: YES, by multiple studies




Does anyone use this for appendicitis?




Excluded: Age <18, injury >7 days old, neuro deficit, distracting injury, paraplegia

Criteria: No X-ray if all of: age<55, patella & fibular head nontender, Can flex 90°, can walk




Excluded: Age <18, injury >10 days old, neuro deficit, intoxication or distracting injury

Criteria: No X-ray needed if malleoli, 5th metatarsal & navicular all non-tender and can walk 4 steps



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Comment from Mark
Time: September 25, 2015, 5:13 pm

1. Wells, Geneva, Clinical gestalt2. Yes. If D-dimer navetige and clinical suspicion high, I image.3. Only patients who are crashing & I suspect saddle embolus AND CV surgeon not available for emergent Trendelenburg procedure.4. I admit all PE’s.

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