Clinical utility of tissue polymerase chain reaction in the diagnosis of spinal tuberculosis

Abstract

BACKGROUND An estimated 14 million people worldwide have active tuberculosis (TB). About 3% of these patients will have osteoarticular involvement and approximately 25% to 60% will have an infectious focus in the spine. Early diagnosis is essential as prompt treatment is associated with improved outcome and reduced mortality. This is particularly true within a high HIV-1 seroprevalence setting. MATERIALS AND METHODS All patients admitted to Kalafong District Hospital from January 2008 to December 2010 with a clinico-radiological diagnosis of spinal TB were included in this study. In all cases Ziehl-Nielsson (ZN) microscopy, TB culture, TB polymerase chain reaction (PCR), and histology with ZN stains were collected, and the turnaround times for these assays recorded. HIV testing was performed on patients who gave consent for the procedure. RESULTS In total, 29 patients were included in this study. Seventeen patients consented to HIV testing of which 11 were confirmed to be positive. It was determined that sensitivity for culture and PCR were comparable at 77% and 72% respectively. Furthermore, when looking at the subgroup of HIV-1 positive patients specifically, both assays performed better, with sensitivities of 88% and 82% respectively. The TAT for assays was highly variable, with PCR and histology having comparable times. CONCLUSIONS PCR testing for spinal TB shows promising results especially within the HIV-1-positive population. Although this type of testing theoretically offers a shorter turnaround time, results were available in similar time frames as for histology. Therefore, on-site testing should be offered in hospitals with high case loads of TB, and combination testing should be used rather than opting for a single testing modality.