Influence of Sputum Quality on PCR Technology for Diagnosis of Pulmonary Tuberculosis

Objective To evaluate the quality of sputum sample in the performance of PCR for diagnosis of pulmonary tuberculosis. Methods Sputum samples were randomly collected from 105 pulmonary tuberculosis patients and 22 non-tuberculosis controls,which were admitted to the Hunan Provincial Tuberculosis Hospital from March to September,2009.The sputum samples were detected by PCR.Those samples that presented more than 40% of viable cells and less than 25% of epithelial cells were defined as high quality samples. Results PCR showed sensitivity of 56.2%,specificity of 54.5%,positive predictive value of 85.5%,negative predictive value of 20.7%,and accuracy of 56.0%.High quality samples showed sensitivity of 74.0%,specificity of 60%,positive predictive value of 94.9%,negative predictive value of 18.8%,and accuracy of 72.7%.Low quality samples showed sensitivity of 40.0%,specificity of 52.9%,positive predictive value of 73.3%,negative predictive value of 22.0%,and accuracy of 43.1%. Conclusions Use of high quality samples improved significantly the PCR performance,especially on their sensitivity and positive predictive values.