Histopathological and microbiological findings and diagnostic performance of GeneXpert in clinically suspected tuberculous lymphadenitis.

OBJECTIVES

The primary objective was to determine the association between histopathological and microbiological findings in patients clinically suspected to have tuberculous lymphadenitis. A secondary objective was to assess the diagnostic utility of GeneXpert in lymph node specimens.

METHOD

This was a single-centre prospective cohort study, performed in the Infectious Disease Clinic at The Indus Hospital. Three hundred and forty-one adult patients with chronically enlarged, accessible lymph nodes were enrolled after obtaining verbal consent, between February 2013 and April 2016. Tissue specimens were processed for histopathology, acid-fast bacillus (AFB) microscopy, AFB culture, and GeneXpert. Based on these results, anti-tuberculosis therapy (ATT) was prescribed. Clinical characteristics and treatment outcomes were recorded.

RESULTS

There were 297 evaluable patients; 74.4% were diagnosed with tuberculous lymphadenitis (TBLA), 6.7% with a malignancy, and 12.8% with reactive nodes. TBLA was diagnosed on suggestive histopathology in 89.6% of cases, followed by GeneXpert (32.6%), mycobacterial culture (26.6%), and AFB smear positivity (12.5%). The sensitivity of GeneXpert was 65.7% when assessed against AFB culture. Drug resistance was displayed by 8.2% of GeneXpert-positive cases and 11.7% of culture-positive cases. The majority of TBLA patients (88.7%) responded favorably to ATT.

CONCLUSIONS

In light of laboratory evidence, a quarter of patients suspected of TBLA had an alternative diagnosis, highlighting its importance in avoiding over-treatment and diagnostic delays in malignancy. Although sensitivity is poor, the demonstration of drug resistance by both GeneXpert and AFB culture represents a useful tool to guide treatment.