Performance of an IS6110-based PCR assay and the COBAS AMPLICOR MTB PCR system for detection of Mycobacterium tuberculosis complex DNA in human lymph node samples

Abstract

We compared the performance of two PCR assays, an IS6110-based in-house protocol and the COBAS AMPLICOR MTB PCR (COBAS MTB) system, for the detection of Mycobacterium tuberculosis complex in 43 human lymph node samples from 40 patients. For the in-house PCR and the COBAS MTB assays, respectively, sensitivities were 87.5% versus 45.5% (P < 0.05), specificities were 100.0% versus 91.3% (P > 0.05), and inhibition rates were 4.8% versus 19.5% (P < 0.05). For the COBAS MTB system, additional N-acetyl-L-cysteine-NaOH pretreatment of the samples changed neither the inhibition rate nor the sensitivity significantly.

FIG. 1.

Sensitivity levels of the in-house PCR assay with detection of amplicons by using an ethidium bromide-stained polyacrylamide gel and DEIA. Lanes: L, 100-bp ladder; 1 through 7, respectively, 10⁵ to 10⁻¹ M. tuberculosis CFU per ml of saline; 8, negative control. +, DEIA positive; −, DEIA negative.