PCR based detection of mycobacteria in paraffin wax embedded material routinely processed for morphological examination

Background-The incidence of mycobacterial infections has increased during t he past five years. A prompt diagnosis is indispensable for initiating appr opriate treatment. Because culturing of mycobacteria takes three to six wee ks and sensitivity of microscopic detection of acid fast bacilli is low, am plification methods provide promising possibilities. Recently, the polymera se chain reaction (PCR) has been shown to be useful for confirming a mycoba cterial infection, especially in cases with unexpected histological finding s or lack of suitable material for culturing. Aims-To evaluate the impact of PCR based techniques in the detection of myc obacterial infections in uncultured routine histological specimens as an al ternative to surgical pathology. Methods-Two hundred and twenty nine formalin fixed and paraffin wax embedde d samples from 141 patients with clinical or histological suspicion of a my cobacterial infection were investigated using three different PCR assays an d Southern blotting. PCR results were compared with histology and culture a nd the patients' clinical findings. Results-When using culture as the reference method, the sensitivity for the detection of mycobacteria of the tuberculosis complex was 90%, specificity was 92%, the positive predictive value was 81%, and the negative predictiv e value was 96%. The sensitivity for the detection of non-tuberculous mycob acteria was 100% and specificity was 78%, the positive predictive value was 26%, and the negative predictive value was 100%. The patients' clinical fi ndings supported the PCR positive results, indicating a mycobacterial infec tion in 11 of 18 initially culture negative cases and in 21 of 35 FCR posit ive cases without culture results. Conclusions-These results indicate that PCR based techniques are sensitive, specific, and rapid methods for the detection of mycobacteria in routinely processed paraffin wax embedded and formalin fixed histological samples.