Kocher Criteria…In a Rush

This week’s 5-minute Journal Article discussion covered

“Validation of a Clinical Prediction Rule for the Differentiation Between Septic Arthritis and Transient Synovitis of the Hip in Children” by Kocher et al.

 

Why is it important to differentiate between septic arthritis and transient synovitis in pediatric patients? Because both diseases can present similarly with acute onset of pain, fever, limp or inability to bear weight and patients holding their hip in the flexed, abducted, externally rotated (FABER) position. The difference is transient synovitis is exactly that, transient, while septic arthritis can lead to permanent joint damage and disability if not treated aggressively with surgical intervention and IV antibiotics.

This study’s goal was to validate the four independent predictors of septic arthritis of the hip in children that Kocher described in his original study, published in 1999 in the Journal of Bone and Joint Surgery, when tested in a new population. The four independent predictors, known as the “Kocher criteria” are:

  1. Fever with temp >38.5C in the past week
  2. Inability to bear weight
  3. Serum WBC > 12,000 cells/mm3
  4. ESR >40mm/hr

According to Kocher’s orginal study, if all 4 of these variables were present, the predicted probability of septic arthritis was as high as 99.6%.

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This validation study ultimately enrolled 213 patients with acutely irritable hip at Boston Children’s hospital, a large tertiary care children’s hospital, between the years of 1997 and 2002. Of the 213 patients, 24 were diagnosed with true septic arthritis (joint fluid with >50,000 wbcs + positive cultures), 27 with presumed septic arthritis (joint fluid with >50,000 wbcs with negative cultures) and 103 with transient synovitis (< 50,000 wbcs in joint fluid, negative cultures, resolution of symptoms without antibiotics and no further disease progression), and 59 were excluded for various reasons.

 

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The diagnostic performance of the prediction rule was analyzed using a Receiver Operating Characteristic Curve and compared to the original study. The area under the curve for the original study was 0.96, whereas the area under the curve for the validation study was 0.86. The authors argued that this diminished performance was expected in this new population as most clinical prediction rules are optimized towards the original study population. However, an area under the curve of 0.86 still shows very good diagnostic performance for a predictive test and because of this, many EM physicians and orthopedic surgeons still use the “Kocher criteria” for septic arthritis today.

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Interestingly, the Kocher criteria does not include CRP as at the time of the study, Boston Children’s Hospital could only test CRP weekly so only about 40% of the participants of the validation study had a documented CRP. Today, it is common to use CRP in addition to serum WBC and ESR when working up a patient for septic arthritis.

5-minute EKG…In a Rush

EKG

Last week’s 5-minute EKG discussion was lead by our APD, Dr. Scott Heinrich.

You get handed this EKG from a patient in triage with chest pain. Should you activate the cath lab?

EKG

 

The answer: No

This EKG is showing left ventricular hypertrophy (LVH) with repolarization abnormality, also known as LVH with strain. This can be easily confused for ischemia, so how do we differentiate between the two?

First and foremost, you must meet criteria for left ventricular hypertrophy. While the gold standard for diagnosing LVH is through echo, there are several different EKG criteria we can use to diagnose LVH, including:

  • S wave depth in V1 + tallest R wave height in V5 or V6 > 35 mm (Sokolov Lyon Criteria)
  • R wave in aVL and S wave in V3 > 20mm (female) or >28mm (male) (Cornell Criteria)
  • R in aVL > 11mm
  • And several other criteria, although these are the most common

 

In LVH, the myocardium becomes thickened, which causes the electricity to move more slowly through the heart. This slowed conduction causes widening of the QRS and repolarization abnormalities. This will appear on EKG as increased R wave peak time of >50ms in leads V5 or V6 and ST depressions with T wave inversions in lateral (left-sided) leads. It is important to note that in LVH with strain, T wave inversions are often asymmetric, in contrast to the symmetric t wave inversions often seen in ischemia.

 

Wellens-Pattern-B-Type-2-T-wave-2

 

 

Ex: Deep, symmetric inverted t waves in Wellen’s (type B)

 

 

 

In summary, in LVH with strain you will see:

  • Lateral leads (I, aVL, V5 – V6) with increased R wave amplitude, time to peak R wave at least 50ms, and ST depressions with asymmetric inverted t waves
  • Inferior and anterior/septal leads with deep S waves and ST elevations in V1-V3 (discordant to deep S)

 

Lastly, here are some tips from EKG guru Amal Mattu that may help to differentiate between LVH with strain and ischemia:

  • If voltage criteria for LVH is not met, assume ischemia
  • Asymmetric T wave inversions favor LVH with strain (although this is NOT always the case, you can have asymmetric TWI in ischemia)
  • Horizontal ST elevations and depressions should be concerning for ischemia

 

Resources:

  1. Life In the Fast Lane – LVH
  2. Amal Mattu ECG weekly – LVH with strain