Value of In-house Viral Transport Medium in Breaking the Bottlenecks for Viral Testing in Pakistan

Abstract

INTRODUCTION: The viral burden of Pakistan has substantially increased over the past decade owing to several outbreaks and newly emerging viruses. In such scenario, maintaining a steady supply of the viral transport medium (VTM) for transporting clinical samples to the laboratory for viral testing is critical. To ensure an adequate supply during times of shortage, we prepared an in-house VTM and validated its capacity to preserve viral nucleic acids. METHODS We used Phosphate-buffered saline (PBS) supplemented with sterile glycerol and a combination of antibiotics viz. vancomycin, colistin sulphate, amphotericin B and trimethoprim lactate, for our VTM formulation. For stability, antimicrobial efficacy and sterility evaluation, representative samples from each batch were selected. To validate our VTM, we tested clinical nasal swab samples transported in commercially available (Copan Italia S.p.A.) and in-house VTM and compared both the media for viral nucleic acid recovery using Reverse transcriptase-polymerase chain reaction (RT-PCR). RESULTS A satisfactory evaluation of in-house VTM in terms of stability, antimicrobial efficacy and sterility was obtained. A total of 239 nasal swabs were processed in both commercial and PBS VTM, out of which 61 samples (25.5%) transported in commercial VTM were positive whereas, 63 samples (26.4%) transported in PBS VTM turned out positive. A comparison of Ct values of samples that exhibited PCR positivity from both groups of VTM (n = 61), showed that 14.7% of samples from PBS VTM as compared to 21.3% of samples from commercial VTM had Ct values of less than 25. Whereas, more samples from PBS VTM (78.7%) as compared to commercial VTM (73.8%) exhibited Ct values of more than 30. No statistical significance was noted for these findings. Our results showed that PBS VTM exhibited 100% sensitivity, 98.9% specificity, 96.8% positive predictive value and 100% negative predictive value. CONCLUSION Our in-house prepared VTM was successfully validated and offers a readily available, cost-effective, and simpler to prepare alternative for diagnostic laboratories in low resource settings, for routine viral testing as well as in preparing for an impending outbreak.