Evaluation of blood PCR in the diagnosis of pulmonary tuberculosis

Culture and specific staining (including Zeil-Nelson and fluorescent methods) are standard measures for the diagnosis of tuberculosis (TB).Because these methods are time-consuming and, sometimes, due to their low accuracy faster and more accurate methods are necessitated. Methods, which can substitute invasive procedures, when obtaining smear samples and culture is not possible; and in addition to being simple and fast, they have an acceptable diagnostic accuracy. The aim of the present study was to verify the diagnostic value of blood PCR in pulmonary TB. This case-control study included 64 proven pulmonary TB cases (according to The National TB Protocol) and 28 subjects who were completely healthy. 4.5ml of blood was derived from each participant and then mixed with 0.5ml EDTA. Finally, DNA extraction and PCR testing using SI 6110 primers was performed for all blood samples. Mean age of the cases and controls was 49.8±18.6 and 48.2±18.5, respectively. 49.2% of the cases and 25% of controls were male. Blood PCR in 23 patients with TB was positive, but none of the controls had a positive PCR (thus, sensitivity of 35.7% and specificity of 100%). With regard to specificity of 100% in PCR method (despite its low sensitivity), in conditions where there is no access to an appropriate specimen, a positive blood PCR can obviate invasive procedures and rapid and definitive diagnosis of the disorder and timely treatment of the patient, his life is saved.