Confidence in polymerase chain reaction diagnosis can be improved by Bayesian estimation of post-test disease probability.

OBJECTIVE: Polymerase chain reaction (PCR) techniques allow highly sensitive detection of specific DNA for diagnosis of infectious and genetic disease, but uncertainty relating to sensitivity and contamination has frequently resulted in controversy over results. We propose a new design in which the PCR contamination rate is estimated experimentally. The sensitivity of duplicate test results, and hence the post-test disease probabilities, can be derived algebraically, but wide confidence limits around these point estimates reduce their usefulness. STUDY DESIGN AND SETTING: We have developed a Bayesian method which gives better estimates of post-test disease probability and can substantially reduce uncertainty by using the prior belief that sensitivity is not lower than 90%. RESULTS: With 100 duplicate test samples and 100 control samples, we find that the post-test disease probability for concordant results (both positive or both negative) is generally unequivocal. The post-test disease probability for discordant results (one test positive and one negative) is often sufficiently clear to allow useful interpretation of individual test results, depending on the context. CONCLUSION: Using this approach, the performance of a PCR can be evaluated experimentally allowing post-test disease probability to be estimated, giving improved confidence in test results.

Limnanthes douglasii lysophosphatidic acid acyltransferases: immunological quantification, acyl selectivity and functional replacement of the Escherichia coli plsC gene.

Antibodies were raised against the two membrane-bound lysophosphatidic acid acyltransferase (LPAAT) enzymes from Limnanthes douglasii (meadowfoam), LAT1 and LAT2, using the predicted soluble portion of each protein as recombinant protein antigens. The antibodies can distinguish between the two acyltransferase proteins and demonstrate that both migrate in an anomalous fashion on SDS/PAGE gels. The antibodies were used to determine that LAT1 is present in both leaf and developing seeds, whereas LAT2 is only detectable in developing seeds later than 22 daf (days after flowering). Both proteins were found exclusively in microsomal fractions and their amount was determined using the recombinant antigens as quantification standards. LAT1 is present at a level of 27 pg/microg of membrane protein in leaf tissue and