§ Mr. RostTo ask the Secretary of State for Health (1) what information he has on accuracy on the assay system currently most commonly used to identify people as HIV antibody positive; and what steps he has taken to ensure that there are no more prospects of people being identified as HIV antibody positive who were subsequently found not to be so;
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Number of newly diagnosed cases of malignant neoplasm of stomach and intestine, usual residents of Mersey regional health authority, England and Wales 1974–84. ICD 151 ICD 152 ICD 153 ICD 154 M E and W M E and W M E and W M E and W 1984 575 11,253 17 327 732 14,840 489 9,577 1983 615 11,553 20 316 642 14,612 417 9,500 1982 617 11,537 13 282 629 14,608 482 9,353 1981 1 537 11,687 20 323 601 14,671 414 9,419 1980 621 11,731 12 285 709 13,843 435 9,280 1979 620 11,904 11 340 671 13,891 457 9,249 1978 657 12,242 15 329 698 14,144 483 9,104 1977 729 12,430 12 341 703 14,115 478 9,056 1976 688 12,235 14 345 662 13,997 474 8,870 1975 725 12,610 17 339 689 13,759 505 8,932 1974 702 12,417 9 304 747 13,580 459 8,711 M=Mersey Regional Health Authority. E and W=England and Wales. International Classification of Diseases (ICD) codes:— ICD 151 Maligant Neoplasm (MN) of Stomach. ICD 152 MN of Small intestine including Duodenum. (2) what checks exist to determine whether people who test first positive and subsequently negative for the presence of HIV antibodies have been subject to inaccurate test procedures or have been able to disable and eliminate the HIV from their systems.
§ Mr. FreemanThe test system most commonly used at present for the detection of HIV antibody has an estimated specificity well in excess of 99 per cent. However, any specimen reacting positively in initial testing should always be retested and referred for further testing with an alternative test system, before any result is issued. With these procedures, true false positives should not occur.
There have been a few recorded instances of people with confimed positive HIV antibody tests who later became seronegative. However, these people may be positive by more direct tests of viral infection suggesting that the explanation is not elimination of HIV, merely failure to produce antibodies.