Screening of specimens by Ziehl-Neelsen staining technique for the diagnosis of extra spinal musculoskeletal tuberculosis: A retrospective study

Abstract

Introduction: Musculoskeletal tuberculosis is a significant form of extra pulmonary tuberculosis (EPTB) which has substantial consequences if not diagnosed and treated early. Reliable and rapid confirmation of the diagnosis is now possible by advent of Polymerase Chain Reaction (PCR), Cartridge Based Nucleic Acid Amplification Test (CB-NAAT/Gene-Xpert) and radiometric method (BACTEC) However, most of these sensitive technologies are not available at places with constrained resources. Hence, diagnosis of tuberculosis at these places, continues to rely on smear microscopy using Ziehl-Neelsen (ZN) staining. Specificity of ZN staining and microscopy is high, but its overall sensitivity is variable (20-53%). Despite of low sensitivity, it is still an easy, cheap, efficient and accessible tool due to its high specificity. Aim: Aim of the present study was to assess the role of ZN staining in diagnosis of extra-spinal musculoskeletal tuberculosis in resource limited settings. Material and methods: A retrospective study was done from 1st January 2016 to 31st December 2019 on specimens received in microbiology laboratory for ZN staining from clinico-radiologically suspected cases of extra-spinal musculoskeletal tuberculosis. The clinical information of the cases was noted from the Orthopaedics Department case files, while results of ZN microscopy were retrieved from the records maintained in Microbiology Department. Results: Specimens from 95 patients with clinico-radiologically suspected extra-spinal musculoskeletal tuberculosis were examined for Acid Fast Bacillus (AFB) by ZN staining technique. Out of 95 patients; 11 patients (11.58 %) were found to be AFB positive. Conclusion: Owing to low yield percentage of ZN staining in extra spinal musculoskeletal tuberculosis; ZN stain alone cannot be used as a tool for diagnosis of this form of tuberculosis.