DETECTION OF MYCOBACTERIUM-TUBERCULOSIS IN FORMALDEHYDE SOLUTION-FIXED, PARAFFIN-EMBEDDED TISSUE BY POLYMERASE CHAIN-REACTION IN POTTS DISEASE

Study Design. Twenty-five formaldehyde solution-fixed, paraffin-embedd ed tissue blocks from vertebral biopsy specimen materials with presump tive diagnosis of tuberculous spondylitis and nonspecific vertebral os teomyelitis were studied. Objectives. To evaluate the sensitivity and specificity of polymerase chain reaction in detecting Mycobacterium tu berculosis in formaldehyde solution-fixed, paraffin-embedded tissue sa mples from histologically proved tuberculous spondylitis. Summary of B ackground Data. Diagnosis of a mycobacterial infection is a long and t edious process; because of the slow growth rate of mycobacteria on sol id media, identification and antibiotic sensitivity testing can take u p to 10 weeks, but the sensitivity of culture can be as low as 50%. Di rect microscopy is insensitive because clinical samples may contain on ly few organisms. Recently, polymerase chain reaction has been applied in the rapid amplification and identification of many organisms, incl uding mycobacteria. Methods. The DNAs were extracted from 25 paraffin- embedded tissue blocks. An insertion element IS 6110 (integrated DNA T ec. Inc., Corrallville, IA), a DNA sequence unique to Mycobacterium co mplex (M. tuberculosis and the subspecies Mycobacterium bovis), was am plified by polymerase chain reaction. Polymerase chain reaction result s were compared with those of Mycobacterium culture, acid-fast bacilli staining, and histologic findings. Results. Polymerase chain reaction was positive in 18 cases of 19 tuberculous spondylitis. Three of the polymerase chain reaction test results were positive with concomitant negative culture and positive acid-fast bacilli staining. There were s ix chronic nonspecific infections, and polymerase chain reaction resul ts were negative in five cases; in the single positive case, DNA ampli fication results remained positive even after three repeated tests. Co nclusion. Polymerase chain reaction has a sensitivity of 94.7%, specif icity of 83.3%, positive predictive value of 94.7%, and a negative pre dictive value of 83.3%. Accuracy was calculated as 92%.