Studies on The Reliability of polymerase chain Reaction as a Tool for the Diagnosis of Mycobacterial organisms in comparison with other Diagnostic Methods

Tuberculosis remains a major problem and its incidence is increasingamong human beings and animals. Diagnosis of tuberculosis by traditional methods lacks sensitivity and specificity and requires up to 10 weeks to be isolated onto solid culture media. Therefore this study was aimed to evaluate PCR as a diagnostic method ft compare between the sensitivity and specificity of traditional methods andthat of PCR.This study was carried out on 100 different specimens derived from60 hospitalized patients and 40 cows suspected of having tuberculosis. Allpatients and animals were subjected to bacteriological testing which included: tuberculin skin test, direct stained smear examination of specimens by Z.N. stain, culture of specimens onto L.J and pyruvic acid ~gg media, and lastly all the specimens were aThe obtained data revealed that the sensitivity of direct smears byZ.N. stain was 77.36% with a specificity of92.16%. Although this method was rapid, specific and easy to be done it didn’t provide information about species of AFB and large number of bacteria (l04/ml) should be present.Culture onto L.J. and pyruvic acid media require about 2 -8 weeks forthe detection of MTBC with a sensitivity and specificity of95.35% and 100% and Positive Predictive Value (PPV) which is probability of diseasein a patient with an abnormal test and Negative Predictive Value (NPV)which is probability of a patient not having the disease when the test resultis negative were 100% and 96.72% respectively.