OBJECTIVETo study the clinical value of combined measurement of C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), lactate dehydrogenase (LDH), and serum ferritin (SF) in the etiological diagnosis of fever of unknown origin (FUO) in children.

METHODSThe clinical data of 154 hospitalized children who had FUO for at least two weeks were retrospectively analyzed, and they were classified into infection (n=54), rheumatism (n=67), and tumor (n=33) groups according to the diagnosis at discharge. The levels of CRP, ESR, LDH, and SF were compared between the three groups, and the diagnostic values of the four indices alone or together were analyzed using the receiver operating characteristic (ROC) curve.

RESULTSSerum CRP and ESR levels were elevated in all the three groups, and increased most significantly in the rheumatism group. Serum LDH level was increased most significantly in the tumor group. SF level was significantly increased in the rheumatism and tumor groups. The area under the ROC curve (AUC) of LDH for diagnosing rheumatism and the AUC of ESR and CRP for diagnosing tumors were lower than 0.7 (P>0.05). The AUC of CRP for diagnosing infection and rheumatism was 0.861 and 0.782, respectively. The AUC of ESR for diagnosing infection and rheumatism was 0.770 and 0.743, respectively. LDH had relatively low AUC, sensitivity, specificity, and Youden's index in diagnosing infection and tumors. SF had the highest AUC, sensitivity, and Youden's index in diagnosing infection, but had the lowest specificity. SF had relatively high AUC, sensitivity, specificity, and Youden's index in diagnosing rheumatism, but had relatively low AUC in diagnosing tumor. The four indices had higher AUC, sensitivity, and specificity in diagnosing rheumatism and tumors when measured together than when measured alone.

CONCLUSIONSIn the etiological diagnosis of FUO in children, CRP, ESR, LDH, and SF have certain clinical significance in the preliminary diagnosis of rheumatic diseases, but have limited value in the diagnosis and differentiation of infectious diseases and malignant tumors. Combined measurement of the four indices is superior to the determination of each one for the etiological diagnosis of FUO in children.