A study of tubercular lymphadenitis: A comparison of various laboratory diagnostic modalities with a special reference to tubercular polymerase chain reaction.

Objective: The purpose of our study was to compare various laboratory diagnostic methods, namely histopathological examination, Ziehl-Neelsen (ZN) stain, AFB culture by conventional Lowenstein-Jensen (LJ) method and fluorescence-based mycobacterial growth indicator tube (MGIT) technique and polymerase chain reaction (PCR) in clinically suspected cases of tubercular lymphadenitis. Materials and Methods: A total of 65 lymph nodes biopsied from patients clinically suspected of having tubercular lymph nodes were included. Specimens were processed for AFB culture after NaOH-NALC concentration and inoculation on LJ medium and using the MGIT system. PCR was performed on all specimens using a commercial nested PCR kit targeting IS6110 insertion element of Mycobacterium tuberculosis complex. All lymph node specimens were subjected to histopathological examination. Results: Of the 65 lymph nodes, 37 (56.9%) were positive on MGIT culture and 45 (69.2%) were positive by PCR. Histopathology showed maximum sensitivity (96%) but with compromised specificity (78.5%). PCR showed 90.1% sensitivity and 100% specificity. The mean turnaround time for mycobacterial growth in smear negative specimens was 30 days determined by LJ and 20 days by MGIT techniques. Conclusion: PCR is a rapid and useful method for diagnosis of TB lymphadenitis and definitely increases the positive predictive value of a positive histopathology report. MGIT is better than LJ culture as regards time to positivity and higher yield.

Rapid ELISA for the diagnosis of rotavirus.

BACKGROUND & OBJECTIVES: Rotavirus is the major cause of gastroenteritis in infants and young children all over the world. The objective of the study was to develop a rapid ELISA for the diagnosis of rotavirus infection in children hospitalised with diarrhoea. METHODS: Immune serum was raised in rabbits by inoculating semipurified rotavirus, SA-11 strain. Immunoglobulins were conjugated to horse radish peroxidase and a rapid ELISA for rotavirus diagnosis was developed. The rapid ELISA was compared with routine ELISA, developed earlier at NIV. RESULTS: Of the 155 faecal samples from patients with diarrhoea, 96 were positive by rapid ELISA and 95 in routine NIV ELISA. OD values were higher in rapid ELISA. The rapid ELISA takes only 4 h to complete. INTERPRETATION & CONCLUSION: Rotavirus diagnosis by rapid ELISA is simple and easy to perform. This may lead to a significant reduction in the unnecessary usage of antibiotics, which cannot control infection due to rotavirus. This technology is being commercialized.