LABORATORY EXPERIENCE AND GUIDELINES FOR AVOIDING FALSE-POSITIVE POLYMERASE CHAIN-REACTION RESULTS

Despite the widespread use of polymerase chain reaction (PCR) for diag nosis of infectious diseases, the technology has not been generally in troduced into routine diagnostic laboratories. One of the most serious problems which has influenced the acceptance of this technology is th e occurrence of false positive PCR results. This study describes the e xperience, in a hospital laboratory setting, of using PCR for the diag nosis of heat-labile enterotoxin-producing E. coli, M. tuberculosis, M . paratuberculosis and human papillomavirus. Results indicate that a b uild-up of amplicons, generated during the amplification process in th e laboratory, is the main source of PCR-contamination. Protocols are d escribed that include both physical and chemical procedures to prevent contamination. The use of photo-induced psoralen is recommended for t hose laboratories already involved in PCR work where amplicons are lik ely to be present. An enzymatic system (uracil-N-glycosylase) was eval uated and is recommended for workers intending to start diagnostic PCR . Attention was given to simple control measures which are easily impl emented in a routine diagnostic laboratory. Protocols such as these ar e likely to have a major impact on the introduction of PCR-based metho ds into routine laboratories.