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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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