XVIII International AIDS Conference


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Evaluation of a PCR in house protocol for the diagnosis of tuberculosis in clinical samples from a public hospital in Guatemala

H. Ortíz Beteta1, B. Samayoa2,3, L. Herlinda1, M.E. Castellanos1, F. Job4, P. Aparicio4, T. Drummond4, T. Villagran1, B. Guzman1, E. Arathoon5, A. Möller1

1Asociación de Salud Integral, Laboratory of Molecular Biology, Guatemala, Guatemala, 2Asociación de Salud Integral, Research and Development, Guatemala, Guatemala, 3Universidad de San Carlos de Guatemala, Microbiology, Guatemala, Guatemala, 4Instituto de Salud Carlos III - Ministerio de Ciencia e Inovación/ACPP, Centro de Medicina Tropical, Madrid, Spain, 5Asociación de Salud Integral, Clinica Familiar 'Luis Angel Garcia', Guatemala, Guatemala

Background: Despite the fact that drugs are available to treat it, Tuberculosis (TB) is still one of the diseases with the highest mortality around the globe. Fast detection and identification of M. tuberculosis (Mtb) is of particular importance in patients co-infected with micobacterioses and HIV. Hospital General San Juan de Dios (HGSJD) is one of the two major public hospitals in the country, providing health services to patients from all regions of Guatemala. Diagnostic techniques with high sensitivity and specificity that provide accurate results in minimum time are required to treat patients in a timely manner. This study was aimed at standardizing a PCR in house protocol for TB diagnosis in clinical samples from a public hospital in Guatemala, and reducing the turnaround time of lab results for TB diagnosis. Methods: 318 samples collected during January to October 2009 in the HGSJD, were analyzed by acid fast stain, culture in Lowenstein Jensen medium (LJ) and PCR. The PCR targeted the IS6110 insertion sequence of Mtb DNA, which allows accurate detection of the Mtb complex. The gold standard was LJ culture, against which microscopy and PCR results were compared.
Results: 44 samples (11.64%) were positive for PCR, representing a sensitivity and specificity of 73.2% (Ic95%: 56.8 - 85.2) and 94.9% (Ic95%: 91.4 -97.1) respectively. When samples were classified as pulmonary and non-pulmonary, the sensitivity and specificity of PCR were 85.7% (Ic95%: 66.4-95.3), 94.1% (Ic95: 89.1-97.0) and 46.2% (Ic95%: 20.4-73.9), 96.2% (Ic95%: 90-98.8) respectively. The turnaround time for the PCR results was 5 days.
Conclusion: The proposed PCR in house protocol can be used for the diagnosis of TB in pulmonary samples. In non-pulmonary samples, the sensitivity and specificity are too low; therefore it is necessary to adjust the conditions of the procedure in order to increase these values.

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