Imprecise usage of the terms "sensitivity" and "specificity" produces confusion in the diagnostic use of sophisticated laboratory test results. "Analytical sensitivity" represents the smallest amount of substance in a sample that can accurately be measured by an assay. "Analytical specificity" refers to the ability of an assay to measure on particular organism or substance, rather than others, in a sample. An assay's analytical sensitivity and analytical specificity are distinct from that assay's clinical diagnostic sensitivity and diagnostic specificity. "Diagnostic sensitivity" is the percentage of persons who have a given disorder who are identified by the assay as positive for the disorder. High analytical sensitivity does not guarantee acceptable diagnostic sensitivity. "Diagnostic specificity" is the percentage of persons who do not have a given condition who are identified by the assay as negative for the condition. False-positive reactions occur because of sample contamination and diminish the diagnostic specificity of the assay. The terms "sensitivity" and "specificity" should be used with the requisite adjectives because the "diagnostic" and the "analytical" meanings of these terms are very different.

"Sensitivity" and "specificity" reconsidered: the meaning of these terms in analytical and diagnostic settings.

It has been shown that mother-to-child human immunodeficiency virus type 1 (HIV-1) transmission can occur both during pregnancy and at delivery, but the respective frequencies in these periods are unknown. Moreover, it is difficult to determine the timing of mother-to-child HIV-1 transmission by direct sampling. The use of an elaborate statistical method is therefore necessary. The authors studied 495 consecutive infants born between May 1988 and August 1991 who were included, at birth, in the French Prospective Study on Pediatric HIV Infection. At least one blood sample was obtained from every infant during the first 14 days of life. All samples obtained within 3 months of birth were tested by at least two of the following methods : viral culture, polymerase chain reaction (PCR), and antigenemia, as well as by Western blot test. Data for the 95 infected infants (those seropositive at 18 months and those who died of HIV disease before this age), and who were exclusively bottle-fed, were analyzed in a Markov model to estimate the timing of viral transmission, the time from birth to the emergence of detectable virus, and the time from birth to seroconversion. The model indicated that one-third of the infants were infected in utero, less than 2 months before delivery (95th percentile). In the remaining 65% of cases (95% confidence interval (Cl) 22-92), the date of infection was estimated as the day of birth. The estimated median period between birth and the emergence of viral markers was 10 days (95% Cl 6-14) and the 95th percentile was estimated at 56 days. These results support the view that HIV infection can be diagnosed during the first 3 months of life. The authors conclude that mother-to-child HIV-1 transmission appears to occur late in pregnancy or at delivery.

http://aj.valleron.free.fr/ajv/selected_publications,_with_pdf_files/costagliola_mereenfant_aje_1995.pdf

Estimated Timing of Mother-to-Child Human Immunodeficiency Virus Type 1 (HIV-1) Transmission by Use of a Markov Model

Objective. —To evaluate human immunodeficiency virus (HIV) type 1—specific cellular immune responses in HIV-seronegative health care workers with occupational high-risk exposures to HIV-infected (HIV-positive) patients. Design. —Peripheral blood mononuclear cells (PBMCs) were obtained after occupational exposures to HIV, and PBMCs from health care workers exposed to HIV-negative patients served as controls. The PBMCs were stimulated in vitro with HIV envelope synthetic peptides. Interleukin 2 (IL-2) production was measured in a bioassay. The HIV antibody status was determined by standard enzyme-linked immunosorbent assays. Exposed individuals were also evaluated for HIV proviral DNA by polymerase chain reaction techniques. Participants. —The PBMCs from eight health care workers with high-risk exposures and nine control health care workers were studied. Results. —The PBMCs from all individuals showed strong IL-2 production to control antigens, indicating intact T-helper function. Interleukin 2 production to HIV peptides was detected in PBMCs from six of eight HIV-exposed individuals, but in only one of the nine health care workers exposed to HIV-negative body fluids ( P Conclusion. —Human immunodeficiency virus—specific T-helper activity was detected in six (75%) of eight HIV-negative health care workers with exposure to HIV-positive body fluids. Potent HIV-specific T-helper activity was detectable 4 to 8 weeks after the exposure and was lost in individuals followed up for 8 to 64 weeks. Three health care workers remained responsive at 8,19, and 24 weeks. Exposure to HIV without evidence of subsequent infection appears to result in activation of cellular immunity without activation of antibody production. ( JAMA . 1994;271:42-46)

https://jamanetwork.com/HttpHandlers/ArticlePdfHandler.ashx?journal=JAMA&articleId=361568&pdfFileName=jama_271_1_035.pdf

HIV-Specific T-Helper Activity in Seronegative Health Care Workers Exposed to Contaminated Blood

HIV replication during the first weeks of life

Background We describe a child who was identified shortly after birth as infected with the human immunodeficiency virus type 1 (HIV-1), but whose infection appears to have completely cleared. Asymptomatic HIV-1 infection was diagnosed in the mother during the fourth month of pregnancy. The infant was delivered vaginally at 36 weeks, received no blood products, and was not breast-fed. Methods and Results HIV-1 was detected by culture of the infant's peripheral-blood mononuclear cells at 19 and 51 days of age. Plasma from the infant was also culture-positive for HIV-1 at 51 days of age by DNA polymerase chain reaction (PCR). Nucleotide-sequence analysis of HIV-1 DNA showed extremely close homology of the cultures obtained 32 days apart, and forensic markers of genetic identity for the two cultures were identical. Hence, inadvertent viral contamination or error in the collection of specimens was highly unlikely. At 12 months of age the infant was seronegative for HIV-1, and numerous subsequent cultures and t...

https://www.nejm.org/doi/pdf/10.1056/NEJM199503303321301

Clearance of HIV Infection in a Perinatally Infected Infant

Polymerase chain reaction (PCR), virus culture (V), antigen detection (Ag), and in vitro antibody production (IVAP) assays may be useful for the early detection of vertically transmitted HIV-1 infection in infants under 18 months of age, when a diagnosis cannot be based on seropositivity because of

Antigen detection, virus culture, polymerase chain reaction, and in vitro antibody production in the diagnosis of vertically transmitted HIV-1 infection

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Antigen detection, virus culture, polymerase chain reaction, and in vitro antibody production in the diagnosis of vertically transmitted HIV-1 infection