Afb Detection Rrna Reflex Rapid Culture Pus

Conventional culture methods can generally detect M tuberculosis in 2 to 3 weeks, although up to 8 weeks of incubation may be required in some instances. This rapid PCR assay detects M tuberculosis complex DNA directly from respiratory specimens and other specimens without waiting for growth in culture and, therefore, the results are available the same day the specimen is received in the laboratory. A mycobacterial culture should always be performed in addition to the PCR assay. The PCR assay is rapid but the culture has increased sensitivity over the PCR assay. The PCR assay targets a unique sequence within the katG gene, which is present in members of the M tuberculosis complex. In addition, the assay can detect genotypic resistance to isoniazid mediated by mutations in the katG target, when present. PCR represents a rapid and sensitive method for the detection of mycobacterial DNA in tuberculous pleural effusions. AFB screening has low sensitivity, and ADA estimation has both low sensitivity and specificity. Therefore, when the clinical suspicion is high and smear result is negative, but the signs and symptoms of M tuberculosis are apparent, PCR is the method of choice for identifying the infection.