Sensitivities of techniques employed in the diagnosis of tuberculosis amongst patients attending directly observed treatment short course clinics in Kano State, Nigeria

Abstract

This study evaluated the effectiveness of different diagnostic methods for diagnosing tuberculosis (TB) amongst patients attending directly observed treatment short course (DOTS) clinics in Kano State, Nigeria. Three diagnostic approaches were employed; smear microscopy using Ziehl-Neelsen (ZN) staining, GeneXpert with the Cepheid GeneXpert system, and Culture with Drug Susceptibility
Testing (DST) on Lowenstein-Jensen medium. Each method provided unique diagnostic insights as smear microscopy confirmed bacterial presence, GeneXpert enabled rapid molecular detection, and culture with DST allowed for comprehensive resistance profiling. A total of 401 TB patients were assessed. The majority were young adults aged 25–34 years (35.4%), with men predominating (71.6%).
Most patients belonged to the Hausa ethnic group (98.8%) and had at least some level of education (94%). Common occupations included self-employment (45.6%) and student status (31.2%).  Diagnostic performance varied considerably. Clinical suspicion and chest radiography achieved 100% sensitivity but 0% specificity, making them useful for initial screening but unreliable for excluding TB
in non-infected individuals. Smear microscopy showed moderate performance with 86.7% sensitivity, 38.7% specificity, and a positive predictive value (PPV) of 66.9%, indicating usefulness mainly for patients with high bacterial loads. GeneXpert demonstrated superior accuracy with 95.4% sensitivity, 95.9% specificity, PPV of 98.7%, and negative predictive value (NPV) of 86.8%, confirming its reliability as a diagnostic tool. Findings underscore GeneXpert as the most effective method in this high-burden setting, offering both rapid and accurate results. However, smear microscopy remains valuable for initial detection in high-bacterial-load cases due to its affordability and availability. While clinical suspicion and radiography are important for preliminary screening, they should be complemented with confirmatory tests. The study recommends integrated screening algorithms combining symptom screening and radiography with confirmatory tests such as GeneXpert, thereby balancing accessibility, accuracy, and cost-effectiveness in TB diagnosis, particularly in resource limited, high-prevalence settings.