INTERLABORATORY COMPARISON OF POLYMERASE CHAIN-REACTION FOR THE DETECTION OF TOXOPLASMA-GONDII DNA ADDED TO SAMPLES OF AMNIOTIC-FLUID

To investigate the accuracy of the polymerase chain reaction (PCR) met hod for the detection of Toxoplasma gondii in clinical specimens, aliq uots of amniotic fluid to which known amounts of Toxoplasma gondii DNA had been added were tested by five European Centres, Four laboratorie s were able to detect DNA at levels equivalent to ten tachyzoites or l ess, including two that detected DNA equivalent to a single parasite, Two laboratories erroneously found one of eight negative control sampl es to be positive, These findings confirm that the high level of sensi tivity associated with the PCR method can be readily achieved under ro utine laboratory conditions, but they also underscore the potential fo r both false-positive and false-negative findings to occur, Furthermor e, the results confirm the urgent need for an external quality assuran ce scheme to support laboratories employing PCR in a clinical context for the detection of Toxoplasma gondii.