PubMed · 3340466
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J T Combs. 1988. Acoustic reflectometry.. https://pubmed.ncbi.nlm.nih.gov/3340466/
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OBJECTIVE: To identify false negative results arising from the use of a commercial kit to detect antibody to HIV-1 and HIV-2 between July 1995 and March 1996. DESIGN: The 56 laboratories in the United Kingdom that were using the assay were asked to retrieve and retest specimens with an alternative assay for HIV-1 and HIV-2. Details of false negative results were obtained and these serum samples further investigated. SUBJECTS: 24,181 patients tested with the assay who were reported as being negative for HIV antibody. An additional 497 patients were confirmed as HIV positive with the assay. RESULTS: Serum samples of 20,973 of the patients were retested, and four patients were found to have had false negative results with the kit; three further patients were found to have had false negative results in the course of other laboratory testing. The seven patients with false negative results with the kit were of diverse risk group and HIV-1 subtype. Four had evidence of recent HIV infection. CONCLUSION: The commercial kit had a sensitivity of 99.2% (497/501), or less if the additional three patients with false negative results were taken into account.
Recent policies of early discharge of postpartum mothers and their infants has raised concerns of possible decreased sensitivity in Guthrie bacterial inhibition assay (BIA) phenylketonuria (PKU) screening resulting in missed cases. In order to assess the potential impact of early discharge from hospital on neonatal screening for PKU and its variants, we performed 18 standard BIA screening tests on 11 newborn infants with the disease. Blood spot samples were collected from 1 to 24 h after birth and were analyzed at the Ontario Ministry of Health newborn screening laboratory according to the routine screening protocol. Except for one 4-hour postnatal sample from an infant with 'non-PKU mild hyperphenylalaninemia' (MHP) all blood samples showed phenylalanine levels > or = 240 mumol/l, irrespective of the age of the baby. During our 29 year experience with neonatal PKU screening (3.9 million infants tested), employing a cutoff blood phenylalanine of 240 mumol/l in blood spots obtained at > or = 24 h of age, only two biological false negative (one confirmed) tests were discovered in infants subsequently shown to have classical PKU: another three false negative tests were discovered in sibs of infants with MHP. The sensitivity of the screening test was 99.2% for infants with classical and mild PKU. Ascertainment of patients with MHP is unknown and is very likely incomplete. Over a 3-year period (1992-4) the specificity of the test was 99.9% for those screened after 24 h. The positive predictive value was 12.8%. Although early discharge may have an impact on other screened diseases, we conclude, from our studies, that early discharge may not affect the detection of infants with classical and mild (atypical) PKU, but would probably increase the number of infants with MHP missed using the BIA and a cutoff level of 240 mumol/l. Because of our experience and that of others, we recommend that neonates be at least 12 h of age before initial BIA PKU screening be carried out. To confirm this recommendation further prospective studies should be initiated.