A non-invasive approach to differential diagnosis of urinary tract infections using lactate dehydrogenase isoenzyme profile, N-acetyl-β-D-glucosaminidase and alanine aminopeptidase

Abstract

Lactate dehydrogenase (LDH) and its isoenzyme profile, Nacety-β-d-glucosaminidase (NAG) and alanine aminopeptidase (AAP) enzyme activities were measured in 21 cases with well documented acute untreated urinary tract infections (UTI) and compared with a group of 68 normal healthy subjects matched for age and sex. Urinary NAG, AAP and LDH total activities were highly elevated (3–30 fold for NAG, 2–10 fold for AAP and 2–50 fold for LDH over upper limit of normal) in upper tract infections. In lower tract infections there was a marginal elevation in NAG and LDH while AAP activity was very high; though there was no overlap. Further, the isoenzyme profile of LDH showed predominance of LD-5 isoenzyme in all cases of pyelonephritis, while it was completely absent in all the cases of lower tract infections. We conclude that urinary NAG and LDH-5 isoenzyme would serve as specific non-invasive parameters for differential localization of urinary tract infections.