Bedside screening of body fluids-Comparison of convenient and conventional methods

Abstract

Background: Reagent strips are used for the rapid diagnosis of pyuria by detection of leukocyte esterase (LE) in the granulocytes. Standard laboratory analysis of body fluids demands expertise, equipment, long turnaround time and availability round-the-clock. Objective: This study intends to evaluate the usefulness of strip in detecting bacterial infection in body fluids other than blood and urine. Methods: The results of strips and standard investigations were compared for 117 fluid samples comprising pleural, ascitic, cerebrospinal, synovial, pericardial fluids, semen, sputum, bronchoalveolar lavage and bronchial wash. Results: The association of LE with total leukocyte count (TLC) and absolute neutrophil count (ANC), sensitivity, negative predictive value (NPV) and diagnostic accuracy (DA) were better as the cut-off value was increased to 250 and 500/μL. The specificity also increased with increasing ANC. The association of LE with nitrite (P = 0.009), neutrophil predominance (P = 0.001), reduced automated glucose level (P = 0.002), glucose estimated by strip with that of autoanalyzer (P = 0.025) were significant. LE was positive in all the samples with bacterial growth in culture. No association was found between LE and occult blood (P = 0.309), protein levels (P = 0.888). Majority of semen samples with round cells, were LE positive, irrespective of the round cell count. Sensitivity and NPV of LE towards combined TLC, reduced glucose and elevated protein were 100% and DA was 66.7%. False positivity and negativity rates were 43.5% and 0% respectively. Conclusion: Reagent strip is useful to screen bacterial infection in body fluids.