Rast et al evaluated biomarkers that can help to differentiate deep vein thrombosis from lower limb erysipelas. This can reduce unnecessary therapy with antibiotics. The authors are from Kantonsspital Aarau and University Hospital Bern in Switzerland.
Patient selection: Emergency Department, diagnosis erysipelas vs deep vein thrombosis (DVT)
Features shared by the 2 conditions: unilateral limb swelling, erythema, pain
Severity of disease was based on systemic inflammatory response syndrome (SIRS) criteria:
(1) temperature < 36°C or > 38.3°C
(2) heart rate > 90 beats per minute
(3) white blood cell count < 4,000 or > 12,000 per microliter
(4) oxygen saturation < 90%
The most useful biomarker for differentiating the two conditions was serum procalcitonin (method Kryptor PCT, Brahms; lower limit of detection 0.02 µg/L). A serum concentration of procalcitonin >= 0.1 µg/L helped to identify a patient with erysipelas, with levels increasing as clinical severity increased.
There was overlap between erysipelas and deep vein thrombosis for C-reactive protein (CRP) and white blood cell count in most cases, although high values tended to be seen with erysipelas. A D-dimer may be positive in infection as well as deep vein thrombosis.
Doppler ultrasonography can be helpful in the patient evaluation but false positive changes can be seen in erysipelas. However, the false positive findings would occur with severe erysipelas which show a high serum procalcitonin level.
Limitations:
• The reference range for procalcitonin was not reported but the upper limit appears to be < 0.1 µg/L.
Performance of procalcitonin:
• The area under the ROC curve was 0.79.
• The presence of concurrent infection affected the performance of procalcitonin.
• A procalcitonin concentration >= 0.1 µg/L had a sensitivity of 58% and specificity of 82% in the absence of concurrent infection (Youden index 0.40).
• A procalcitonin concentration >= 0.1 µg/L had a sensitivity of 63% and specificity of 75% in the presence of concurrent infection (Youden index 0.38).
• A procalcitonin concentration > 0.5 µg/L was highly specific in the presence of concurrent infection.
