Diagnostic performance of Ziehl-Neelsen staining and Auramine-Rhodamine staining techniques in the detection of pulmonary and extrapulmonary tuberculosis.

Background: Motivation for the study. Peru has a high prevalence of tuberculosis, therefore, it is necessary to use diagnostic methods with high sensitivity and specificity to adequately identify cases and provide timely treatment. Main findings. Our results indicate that, when comparing the smear microscopy techniques commonly used in Peru with the molecular tests recommended by the WHO, direct microscopy techniques show low sensitivity, less than 50%, but high specificity, greater than 95%. Implications for public health. It is necessary to evaluate the implementation and associated costs of new rapid diagnostic alternatives that have adequate capacity to identify the majority of tuberculosis cases.

Objective.: To determine the diagnostic performance of Ziehl-Neelsen and Auramine-Rhodamine staining for pulmonary and extrapulmonary tuberculosis.

Materials and methods.: This was a cross-sectional diagnostic test study. We used a database of processed samples from patients with suspected pulmonary and extrapulmonary tuberculosis in a private laboratory in Peru between 2011 and 2022. Ziehl-Neelsen staining and Auramine-Rhodamine staining were the index tests. The reference tests were Xpert MTB/RIF and Xpert Ultra. The receiver operating characteristics and area under the curve (AUC/ROC) were calculated to determine the diagnostic performance of each staining technique.

Results.: We analyzed 908 samples processed by Ziehl-Neelsen staining and 623 samples by Auramine-Rhodamine staining, most were lung tissue samples. Using the Xpert MTB/RIF as a reference test, the Ziehl-Neelsen staining obtained an AUC=0.72, a sensitivity of 44.2% and specificity of 99.3%; and Auramine-Rhodamine staining showed an AUC=0.73, a sensitivity of 46.8% and specificity of 100%. Considering the Xpert Ultra test as a reference, the diagnostic performance for Ziehl-Neelsen showed an AUC=0.63 with a sensitivity of 26.9% and specificity of 98.5%; and an AUC=0.64 with a sensitivity of 30% and specificity of 98.2% for the Auramine-Rhodamine staining.

Conclusion.: The diagnostic performance for both staining techniques is fair, and decreases when taking Xpert Ultra as a reference. New diagnostic alternatives with adequate performance are needed to detect tuberculosis.