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Fever, weightbearing, sedimentation rate best for diagnosing hip infection.

* CLINICAL QUESTION

How can I differentiate septic arthritis from transient synovitis of the hip in children?

* BOTTOM LINE

To distinguish septic arthritis from transient synovitis of the hip in children, the following factors are very helpful: a history of fever, inability to bear weight, erythrocyte sedimentation rate higher than or equal to 40 mm/hour, and a peripheral white blood cell count greater than 12,000/[mm.sup.3]. (LOE: 1a)

* STUDY DESIGN

Decision rule (validation)

* SETTING

Outpatient (specialty)

* SYNOPSIS

A total of 154 consecutive children with intact immune systems and no recent surgery presenting to a tertiary care center with an acutely irritable hip were evaluated in a systematic manner: history, physical, laboratory assessment, x-rays, joint fluid analysis, and so forth. Although C-reactive protein tests have been shown to be better than erythrocyte sedimentation rate in the diagnosis of septic arthritis in children, C-reactive protein tests were not readily available early in this study and therefore were not included in data analysis to avoid any potential bias.

The researchers used explicit diagnostic standards. A truly septic joint was defined as a positive joint fluid culture or a white blood cell count in the joint fluid of 50,000 cells/[mm.sup.3] or higher plus a positive blood culture. The authors presumed the patient had septic arthritis when the patient had a white blood cell count in the joint fluid of >50,000 cells/[mm.sup.3] with negative cultures of the joint aspirate and blood. The researchers combined these 2 groups to constitute septic arthritis. They defined transient synovitis as having a white blood cell count in the joint fluid of <50,000 cells/[mm.sup.3] with negative culture, resolution of symptoms without antibiotics and no subsequent evolution of symptoms during a mean follow-up of 11.8 months.

In a previous study, a set of 4 factors were found to differentiate the septic joints from those with transient synovitis: a history of fever, an inability to bear weight, an erythrocyte sedimentation rate higher than or equal to 40 mm/hour, and a peripheral white blood cell count of >12,000 cells/[mm.sup.3]. These same variables performed well here.

The sensitivity, specificity, positive likelihood ratio, and negative likelihood ratio are, respectively, as follows: 1 factor (100%, 26%, 1.4, infinity); 2 factors (90%, 68%, 2.8, 0.15); 3 factors(59%, 89%, 5.4, 0.5); and all 4 factors (16%, 99%, 16, 0.8). The area under the receiver operating characteristic curve, a measure of overall diagnostic accuracy, was 0.86.

Kocher MS, Mandiga R, Zurakowski D, Barnewolt C, Kasser JR. Validation of a clinical prediction rule for the differentiation between septic arthritis and transient synovitis of the hip in children. J Bone Joint Surg (Am) 2004; 86:1629-1635.

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Title Annotation:Practice Recommendations from Key Studies
Author:Kocher, M.S.; Mandiga, R.; Zurakowski, D.; Barnewolt, C.; Kasser, J.R.
Publication:Journal of Family Practice
Geographic Code:1USA
Date:Nov 1, 2004
Words:464
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