Bronchoalveolar Wash: Proposal of a Cutting Point for Lactate Dehydrogenase in the Differential Diagnosis of Pulmonary Diseases

Abstract

Background: The analysis of bronchoalveolar lavage (BAL) is of great clinical utility in the diagnosis of pulmonary diseases (PDs). The cytological study (total and differential cell count) performed routinely in these samples, has a high orientative power and is diagnostic in some cases. The study of soluble substances has provided little information. This study aimed to determine the cut-off point of lactate dehydrogenase (LDH) activity in the diagnosis of different lung diseases.

Methods: Two hundred forty-three BALs were selected from a total of 306 patients with a single respiratory disease: acute pneumonia due to common germs (NCG, n = 126), tuberculosis (TB, n = 20), mycotic pneumonia (MN, n = 12, N = 37) and interstitial diseases (IDs, n = 48). Cytological study and measurement of LDH activity were performed. The mean, standard deviation, sensitivity (S), specificity (Sp) and Youden index (YI) of this enzyme were determined. Student’s parametric and non-parametric Mann-Whitney tests were done (P < 0.05: significant).

Results: Comparing the means and standard deviations of LDH in the different PDs, a significant increase of this parameter was observed in the NCG compared to the other PDs: NCG vs. TB (P = 0.003); MN, MD and ID (P < 0.0001). Based on these significant differences observed, the cut-off point for LDH in NCG was evaluated. Different values were analyzed: LDH: ≥ 150 IU/L with S: 70%, Sp: 85% and YI: 0.55; ≥ 130 IU/L with S: 77%, Sp: 80% and YI: 0.57; ≥ 120 IU/L with S: 80%, Sp: 77% and YI: 0.57 and ≥ 100 IU/L with S: 86%, Sp: 74% and YI: 0.60.

Conclusions: It is proposed to perform the measurement of LDH activity for the differential diagnosis of NCG in the PD, since its mean value was significantly higher than the rest of the PD, using a cut-off point of LDH ≥ 100 IU/L; it showed a higher S and YI for the diagnosis of NCG screening. Increased LDH activity in NCG could be associated with the high number of leukocytes present in this pathology, superior to the rest of the PD. Measurement of LDH activity along with cell count would contribute to the diagnosis of PD.




Clin Infect Immun. 2017;2(1):1-4
doi: https://doi.org/10.14740/cii60e