Comparison of White Blood Cell Count, Erythrocyte Sedimentation Rate, and C-Reactive Protein for Diagnosis of Diabetic Foot Infection

Lee, Joon Moon; Han, Seung Kyu; Gu, Ja Hea; Jung, Sung Ho; Kim, Woo Kyung

Abstract

PURPOSE
Diagnosis of diabetic foot infection is sometimes difficult, since the classical inflammatory signs and leukocytosis may be absent due to the decreased host immune response in diabetics. Therefore inflammatory blood markers, such as white blood cell(WBC) count, erythrocyte sedimentation rate(ESR), and C-reactive protein(CRP) have been commonly needed to confirm the diagnosis of infection. The purpose of this study is to evaluate the diagnostic usefulness of WBC, ESR and CRP for detection of diabetic foot infection.
METHODS
Peripheral blood samples were taken from 113 patients with diabetic foot ulcers admitted from June 2007 to April 2009. Diabetic foot infection was diagnosed according to the microbiological culture from soft tissue and bone specimens. Reference values of tests were 4500-11000/microliter for WBC count, 0-20mm/hr for ESR, and 0-5 mg/L for CRP(13,14). Sensitivities, specificities, positive and negative predictive values of laboratory tests were calculated and analysed. Receiver-operator characteristic (ROC) curve was also created.
RESULTS
There was a significant difference in WBC, ESR, and CRP between infectious group and noninfectious group(p<0.05). The sensitivity of WBC>11,000/microliter ESR >20 mm/hr, and CRP > 5mg/L was 30%, 96%, and 84%. The specificity was 86%, 14%, and 50% for WBC, ESR, and CRP, respectively. Positive predictive value was 88%, 78%, and 84%, and negative predictive value was 28%, 50%, and 50% respectively. The areas under the ROC curve for WBC, ESR and CRP were 0.72, 0.75, and 0.78 respectively.
CONCLUSION
Based on the results of this study, we conclude that CRP is more useful method in predicting and diagnosing infection than WBC, ESR in diabetic foot ulcer patients.