Diagnóstico de la infección por Treponema pallidum en pacientes con sífi lis temprana y neurosífi lis mediante reacción de la polimerasa en cadena Patricia García C., Bruno Grassi C., Félix Fich S., Aurelio Salvo L., Luis Araya C., Fernando Abarzúa C., Julia Soto M., Helena Poggi M., Marcela Lagos L., Patricia Vásquez T., Eugenia P. León C., Carlos Pérez C. y Aniela Wozniak B. Laboratory diagnosis of Treponema pallidum infection in patients with early syphilis and neurosyphilis through a PCR-based testSyphilis is a sexually transmitted disease caused by Treponema pallidum. The diagnosis is based mainly in clinical presentation and non-specifi c assays. PCR-based diagnosis has been suggested as an attractive alternative method. The aim of this study was the validation of a PCR-based test for the diagnosis of early syphilis (ES) and neurosyphilis (NS). Clinical samples of mucocutaneous lesions and cerebrospinal fl uid (CSF) specimens from patients previously diagnosed for ES and NS respectively using an enlarged gold standard, were tested by PCR. The reaction was done using primers targeting the tpN47gene. Twenty out of 21 mucocutaneous samples from patients diagnosed with ES were positive by PCR, with a clinical sensitivity of 95%. Four out of 8 CSF samples from patients previously diagnosed with NS were positive by PCR, with a clinical sensitivity of 50%. The clinical specifi city for both ES and NS was 100%. The PCR sensitivity and specifi city for mucocutaneous samples allowed us to implement this assay in our laboratory for routine diagnosis. Although the sensitivity of the PCR in CSF was low, it may be useful to support clinical diagnosis.Key words: Treponema pallidum, syphilis, polymerase chain reaction, diagnosis. Palabras clave: Treponema pallidum, sífi lis, reacción de polimerasa en cadena, diagnóstico. Pontificia Universidad Católica de ChileDepartamento de Laboratorios Clínicos:Laboratorio de Microbiología (PGC, EPLC, AWB).Unidad Docente de Apoyo:División Ginecología y Obstetricia (FAC). Laboratorio de Biología Molecular(JSM, HPM, MLL).Departamento de Medicina Interna (CPC). Escuela de Medicina (BGC).Hospital San Juan de Dios, Santiago. Servicio de Neurología (LAC). Unidad de Infectología (PVT).Hospital Sótero Del Río, Santiago. Introducción L a sífi lis es una enfermedad de transmisión sexual, de carácter crónico, que evoluciona en fases clíni-cas: sífi lis primaria, secundaria, latente y terciaria. El agente etiológico de la sífi lis, Treponema pallidum, es una espiroqueta no cultivable 1 . Durante los últimos años se han registrado brotes de esta enfermedad en varios países, incluso en naciones desarrolladas como Canadá (National Infectious Disease Examiner.com -Syphilis spikes in Alberta, Canada-health offi cials looking for solutions. URL: http://www.examiner.com). En Alberta, una provincia de Canadá, existe una gran preocupación debido a que el número de casos de sífi lis en 1999 fue dos y en 2009 ascendió a 267 casos, probablemente debido a la promiscuidad sexual de las personas, principalmente ...
Assessment of the Amplicor PCR® for the detection of Mycobacterium tuberculosis in smear negative respiratory and non respiratory specimens: A retrospective analysis Background: Commercial polymerase chain reaction (PCR) kits are widely accepted for analysis of smear positive respiratory specimens, but the sensitivity is variable for smear negative ones. Objective: To assess the PCR method usefulness in smear negative respiratory and non respiratory specimens. Methods: We compared the PCR results (AMPLICOR MTB test™, Roche) of 235 specimens subjected to culture in Loewenstein-Jensen agar (as the gold standard). Results: 181 (76%) were respiratory and 54 (24%) extra-respiratory specimens. The sensitivity was 88% and 50%, respectively, specificity and PPV was 100% in both cases. NPV was 99.4% in respiratory specimens and 96.1% in non-respiratory specimens. Conclusions: The good performance of this PCR in smear negative respiratory specimens allows the clinician to take decisions based on the result of this exam. In extra-respiratory specimens the contribution is important only when the PCR result is positive.
Universal or broad-range polymerase chain reaction (PCR): A contribution to the detection and identification of bacteria and fungi in clinical practice (Rev Méd Chile 2009; 137: 1122-5
The knowledge of the human genome has led to an explosion of available genetic tests for clinical use. The methodologies used in these tests vary widely, allowing the study from chromosomes to the analysis of a single nucleotide. Prior to its use in the clinical setting, these tests should have an evaluation that includes analytical and clinical validation and determination of the clinical utility, as any other tests, including requirements for quality assurance. Recently, the CDC (Centers for Disease Control and Prevention, USA) published a guideline for Good Laboratory Practices for Molecular Genetic Testing for Heritable Diseases and Conditions, covering the preanalytical, analytical and postanalytical phases of the tests. The document covers the importance of proper selection of tests, the availability of information on the performance of the techniques used, the quality control practices, the training of personnel involved and the report of results, to allow the adequate interpretation, including sensitivity and specificity. Considering that recent advances in genetics have changed and will continue to affect clinical practice, genetic tests must meet quality and safety requirements to enable optimal use of them.
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