Ziehl-Neelsen stain in the pathology laboaratory: Performance and diagnostic aid for mycobacteria in bronchoalveolar...

Introduction: With more than 100 years of use, the Ziehl-Neelsen stain is still currently used worldwide. Objective: To compare the performance of diagnostic tests used to determine mycobacteria in the clinic and pathology laboratory in bronchoalveolar lavage samples. Materials and methods: We retrospectively reviewed 737 bronchoalveolar lavage samples from 2019 to 2020 in the San Vicente Fundación hospital (Medellín, Colombia) comparing the performance of three tests done in parallel: mycobacteria and resistance PCR, culture, and Ziehl-Neelsen stain. Results: In total, 93/737 patients were classified as sick due to a positive result in any of the three tests. The culture, PCR, and Ziehl-Neelsen stain had a sensibility of 0.80, 0.76 y 0.51, respectively. However, only 5/75 (6.5%) of the positive cultures had results within the first four weeks and the rest in eight weeks. The PCR test combined with the Ziehl-Neelsen stain improved the sensibility of the PCR test alone from 0.76 a 0.88, a change that was statistically significant (p = 0.022). Conclusion: At least in bronchoalveolar lavage samples, culture is still the test with better sensibility. The use in parallel of the PCR test and the Ziehl-Neelsen stain improved in a statistically significant manner the performance of the PCR test alone, regardless of the higher turnaround time of the Ziehl-Neelsen stain.