Serum lactate dehydrogenase isoenzymes 4 plus 5 is a better biomarker than total lactate dehydrogenase for refractory Mycoplasma pneumoniae pneumonia in children

Although usually self-limiting, Mycoplasma pneumoniae pneumonia (MPP) may lead to clinical or radiological deterioration despite macrolide antibiotic therapy, resulting in the development of refractory MPP (RMPP). Corticosteroids have been used to treat RMPP with beneficial effects. Serum lactate dehydrogenase (LDH) is a suggested biomarker for the use of steroid therapy. Since serum LDH is a non-specific marker and elevated in many inflammatory processes, this study investigates the predicting level of LDH isoenzymes for RMPP. Fifty-four children with non-refractory M. pneumoniae pneumonia (NRMPP) and 16 children with RMPP were enrolled in this study. In comparison to the NRMPP group, the RMPP group showed significantly higher levels of serum LDH. Concerning LDH isoenzymes, the RMPP group showed significantly lower proportions of LDH1 and LDH2, while higher LDH4 and LDH5 percentage. Receiver operating characteristic curve analysis showed that the area under the curve for the total LDH data was 0.812 with a cut-off of 408 IU/L (sensitivity of 75.0%, specificity of 72.2%). The areas under the curve for LDH4, LDH5, and [LDH4 + LDH5] were estimated to be 0.813, 0.818, and 0.829, respectively. The threshold for [LDH4 + LDH5] was estimated to be 109.4 IU/L (sensitivity, 75.0%; specificity, 87.0%). These results indicate that for the initiation of corticosteroid therapy, serum [LDH4 + LDH5] level is a more sensitive biomarker than total LDH. Key Words: children, LDH isoenzyme, refractory Mycoplasma pneumoniae pneumoni