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Sensitivity and specificity of various diagnostic tests in the detection of Helicobacter pylori.

OBJECTIVE
This study was conducted to detect the sensitivity and specificity of various diagnostic tests on biopsy specimens obtained from patients undergoing elective endoscopy, by culture, histopathology (special stain), urease (biochemical test) and the presence of specific antibodies by serology for the detection of Helicobacter pylori.


PLACE AND DURATION OF STUDY
This study was conducted in Civil Hospital, Karachi, in collaboration with Dr. Essa Laboratories and IIDRL (Immunology and Infectious Disease Research Laboratory), Karachi University, from June 99-to July 2000.


SUBJECTS AND METHODS
Biopsy material was taken from 50 patients referred for elective endoscopy with symptoms of various upper gastrointestinal diseases. Non-endoscopic methods serology and endoscopic biopsy specimens using urease test, by culture and histopathology using special stain, detected presence of H. pylori. Sensitivity and specificity was calculated using the standard formula, only those cases were taken as true positive which were positive by either culture test and/or special stain. Those cases giving positive results only by serology or urease test not supported by either of the direct tests were taken as false positive


RESULTS
The percentage of positive cases detected was 81% by serology, 80% by histopathology, 9% by culture and 56% by urease test. Sensitivity and specificity was by serology 84% and 60%, histopathology (special stain) 83% and 100%, culture 64% and 100% and by urease test 67% and 85% respectively.


CONCLUSION
H. pylori infection can be detected by a variety of methods. The simplest and least expensive method is serology. Positive serology does not distinguish between active and chronic infection and is less specific as compared to other methods. Histopathology (special stain) allows simultaneous evaluation of tissue injury and has a high degree of sensitivity and specificity. Culture can be used to detect antibiotic resistant organisms.