Final Recommendation Statement
Human Immunodeficiency Virus (HIV) Infection: Screening, 2005
July 05, 2005
Recommendations made by the USPSTF are independent of the U.S. government. They should not be construed as an official position of the Agency for Healthcare Research and Quality or the U.S. Department of Health and Human Services.
This Recommendation is out of date
It has been replaced by the following: Human Immunodeficiency Virus (HIV) Infection: Screening (2019)
- Update in Progress for Human Immunodeficiency Virus (HIV) Infection: Screening
|Adolescents and adults at increased risk for HIV infection||The U.S. Preventive Services Task Force (USPSTF) strongly recommends that clinicians screen for human immunodeficiency virus (HIV) all adolescents and adults at increased risk for HIV infection (go to Clinical Considerations for discussion of risk factors). Rationale: The USPSTF found good evidence that both standard and U.S. Food and Drug Administration (FDA)-approved rapid screening tests accurately detect HIV infection. The USPSTF also found good evidence that appropriately timed interventions, particularly highly active antiretroviral therapy (HAART), lead to improved health outcomes for many of those screened, including reduced risk for clinical progression and reduced mortality. Since false-positive test results are rare, harms associated with HIV screening are minimal. Potential harms of true-positive test results include increased anxiety, labeling, and effects on close relationships. Most adverse events associated with HAART, including metabolic disturbances associated with an increased risk for cardiovascular events, may be ameliorated by changes in regimen or appropriate treatment. The USPSTF concluded that the benefits of screening individuals at increased risk substantially outweigh potential harms||A|
|Pregnant women||The USPSTF recommends that clinicians screen all pregnant women for HIV. Rationale: The USPSTF found good evidence that both standard and FDA-approved rapid screening tests accurately detect HIV infection in pregnant women and fair evidence that introduction of universal prenatal counseling and voluntary testing increases the proportion of HIV-infected women who are diagnosed and are treated before delivery. There is good evidence that recommended regimens of HAART are acceptable to pregnant women and lead to significantly reduced rates of mother-to-child transmission. Early detection of maternal HIV infection also allows for discussion of elective cesarean section and avoidance of breastfeeding, both of which are associated with lower HIV transmission rates. There is no evidence of an increase in fetal anomalies or other fetal harm associated with currently recommended antiretroviral regimens (with the exception of efavirenz). Serious or fatal maternal events are rare using currently recommended combination therapies. The USPSTF concluded that the benefits of screening all pregnant women substantially outweigh potential harms.||A|
|Adolescents and adults who are not an increased risk for HIV infection||The USPSTF makes no recommendation for or against routinely screening for HIV adolescents and adults who are not at increased risk for HIV infection (go to Clinical Considerations for discussion of risk factors). Rationale: The USPSTF found fair evidence that screening adolescents and adults not known to be at increased risk for HIV can detect additional individuals with HIV, and good evidence that appropriately timed interventions, especially HAART, lead to improved health outcomes for some of these individuals. However, the yield of screening persons without risk factors would be low, and potential harms associated with screening have been noted (above). The USPSTF concluded that the benefit of screening adolescents and adults without risk factors for HIV is too small relative to potential harms to justify a general recommendation.||C|
|Table of Contents||PDF Version and JAMA Link||Archived Versions|
Recommendations made by the USPSTF are independent of the U.S. government. They should not be construed as an official position of the Agency for Healthcare Research and Quality or the U.S. Department of Health and Human Services.
In September 2006, the Centers for Disease Control and Prevention (CDC) published revised guidelines recommending that all individuals between 13 and 64 yeas of age be screened for HIV regardless of recognized risk factors (1). In making this recommendation, the CDC considered a number of factors, including research published subsequent to the completion of the systematic evidence report on which the 2005 HIV screening recommendations of the USPSTF are based.
In November 2006, the USPSTF assessed this new research using established methods for evaluating the quality and strength of the evidence (2). Based on this review (3), the USPSTF confirmed its "C" recommendation for screening non-pregnant adolescents and adults who are not at increased risk for HIV infection.
- Centers for Disease Control and Prevention. Revised recommendations for HIV testing of adults, adolescents, and pregnant women in health-care settings. MMWR 2006;55(RR-14):1-17
- Harris RP, Helfand M, Woolf SH, et al. Current methods of the third U.S. Preventive Services Task Force. Am J Prev Med 2001;20(3S):21-35
- Chou R, Huffman L. Screening for human immunodeficiency virus: focused update of 2005 systematic evidence review. April 2007.
- The USPSTF recommends that clinicians screen all pregnant women for HIV.
Rating: A Recommendation.
Rationale: The USPSTF found good evidence that both standard and FDA-approved rapid screening tests accurately detect HIV infection in pregnant women and fair evidence that introduction of universal prenatal counseling and voluntary testing increases the proportion of HIV-infected women who are diagnosed and are treated before delivery. There is good evidence that recommended regimens of HAART are acceptable to pregnant women and lead to significantly reduced rates of mother-to-child transmission. Early detection of maternal HIV infection also allows for discussion of elective cesarean section and avoidance of breastfeeding, both of which are associated with lower HIV transmission rates. There is no evidence of an increase in fetal anomalies or other fetal harm associated with currently recommended antiretroviral regimens (with the exception of efavirenz). Serious or fatal maternal events are rare using currently recommended combination therapies. The USPSTF concluded that the benefits of screening all pregnant women substantially outweigh potential harms.
In 1996, the USPSTF recommended routine counseling and screening for all persons at increased risk for HIV infection (an A Recommendation) and routine counseling and screening for high-risk pregnant women, as well as those residing in communities where the prevalence of seropositive newborns is increased (an A Recommendation).1. At that time, the USPSTF found insufficient evidence to recommend for or against routine HIV screening for persons without identified risk factors (a C Recommendation) and insufficient evidence to recommend for or against universal prenatal screening in low-prevalence communities (a C Recommendation). Testing infants born to high risk mothers was recommended when the antibody status of the mother is unknown (a B Recommendation). Since then, the USPSTF approach to making recommendations has changed2 and significant new evidence on screening for and treating HIV infection has been published in the medical literature. Therefore, in 2005, a revised and updated recommendation statement was published, based on a new review of the literature, and using the USPSTF methodology in effect in 2005.
In November 2006, the USPSTF assessed new findings from the CDC and confirmed its C Recommendation for screening non-pregnant adolescents and adults who are not at increased risk for HIV infection.
A person is considered at increased risk for HIV infection (and thus should be offered HIV testing) if he or she reports 1 or more individual risk factors or receives health care in a high-prevalence or high-risk clinical setting.
Individual risk for HIV infection is assessed through a careful patient history. Those at increased risk (as determined by prevalence rates) include: men who have had sex with men after 1975; men and women having unprotected sex with multiple partners; past or present injection drug users; men and women who exchange sex for money or drugs or have sex partners who do; individuals whose past or present sex partners were HIV-infected, bisexual, or injection drug users; persons being treated for sexually transmitted diseases (STDs); and persons with a history of blood transfusion between 1978 and 1985. Persons who request an HIV test despite reporting no individual risk factors may also be considered at increased risk, since this group is likely to include individuals not willing to disclose high risk behaviors.
There is good evidence of increased yield from routine HIV screening of persons who report no individual risk factors but are seen in high-risk or high-prevalence clinical settings. High-risk settings include STD clinics, correctional facilities, homeless shelters, tuberculosis clinics, clinics serving men who have sex with men, and adolescent health clinics with a high prevalence of STDs. High-prevalence settings are defined by the Centers for Disease Control and Prevention (CDC) as those known to have a 1% or greater prevalence of infection among the patient population being served. Where possible, clinicians should consider the prevalence of HIV infection or the risk characteristics of the population they serve in determining an appropriate screening strategy. Data are currently lacking to guide clinical decisions about the optimal frequency of HIV screening.
Current evidence supports the benefit of identifying and treating asymptomatic individuals in immunologically advanced stages of HIV disease (CD4 cell counts < 200 cells/mm3) with HAART. Appropriate prophylaxis and immunization against certain opportunistic infections have also been shown to be effective interventions for these individuals. Use of HAART can be considered for asymptomatic individuals who are in an earlier stage of disease but at high risk for disease progression (CD4 cell count < 350 cells/mm3 or viral load > 100,000 copies/mL), although definitive evidence of a significant benefit of starting HAART at these counts is currently lacking.
The standard test for diagnosing HIV infection, the repeatedly reactive enzyme immunoassay followed by confirmatory western blot or immunofluorescent assay, is highly accurate (sensitivity and specificity > 99%). Rapid HIV antibody testing is also highly accurate; can be performed in 10 to 30 minutes; and, when offered at the point of care, is useful for screening high risk patients who do not receive regular medical care (e.g., those seen in emergency departments), as well as women with unknown HIV status who present in active labor.
Early identification of maternal HIV seropositivity allows early antiretroviral treatment to prevent mother-to-child transmission, allows providers to avoid obstetric practices that may increase the risk for transmission, and allows an opportunity to counsel the mother against breastfeeding (also known to increase the risk for transmission). There is evidence that the adoption of "opt-out" strategies to screen pregnant women (who are informed that an HIV test will be conducted as a standard part of prenatal care unless they decline it) has resulted in higher testing rates. However, ethical and legal concerns of not obtaining specific informed consent for an HIV test using the "opt-out" strategy have been raised. While dramatic reductions in HIV transmission to neonates have been noted as a result of early prenatal detection and treatment, the extent to which detection of HIV infection and intervention during pregnancy may improve long-term maternal outcomes is unclear.
Of the estimated 850,000 to 950,000 persons in the United States infected with HIV-1, 25% are thought to be unaware of their status.3,4 If untreated, almost all infected individuals will eventually develop acquired immunodeficiency syndrome (AIDS), defined by opportunistic infection or severe immune dysfunction. Despite significant recent advances in treatment, AIDS is the seventh leading cause of death in persons aged 15 to 24 years, and the fifth leading cause of death in persons aged 25 to 44 years in the United States.5
HIV incidence rates (an estimated 40,000 new infections annually) have remained steady in the United States over the last decade.6 This figure includes infection via mother-to-child (vertical) transmission, with approximately 300 infants infected each year. Women are the fastest-growing group of persons with new HIV diagnoses, and an estimated 6,000 to 7,000 HIV-positive women give birth each year in the United States.7,8 Effective interventions are available to reduce rates of vertical transmission for women diagnosed with HIV infection. However, in 2000, 40% of infected infants were born to mothers not known to have HIV infection before delivery.9
To update its 1996 recommendations on HIV screening, the USPSTF examined the evidence from 1983 through June 2004 on the benefits and harms of screening and of currently available interventions for HIV infection in adults, adolescents, and pregnant women. Relevant studies on risk factor assessment and the accuracy and acceptability of testing were also reviewed.
The USPSTF review found that standard testing for HIV infection has a sensitivity and specificity greater than 99% and that false-positive test results are rare, even in low risk settings.10,11 While indeterminate results may occur a little more frequently among parous and pregnant women, the diagnostic accuracy of standard HIV testing is thought to be similar for pregnant women and non-pregnant women and men.12 Alternative FDA-approved screening technologies are also highly accurate and may increase testing acceptability. Compared with standard HIV testing, the reported sensitivities of rapid tests on blood specimens range from 96% to 100%, with specificities greater than 99.9%.13-15 Reported sensitivities and specificities of oral fluid HIV tests are also high (> 99%), although the diagnostic accuracy of urine tests appears lower than that of standard testing.16,17 One good-quality study of the only FDA-approved home collection kit, using finger-stick blood spot samples, found it to be highly accurate compared with standard testing.18
A large, good-quality U.S. study found that risk factor assessment can identify individuals at substantially higher risk for HIV, but still misses a significant proportion (20% to 26%) of HIV-positive clients who report no risk factors19 (since some patients may choose not to disclose high risk behaviors and others, especially women, may be unknowingly at risk from an infected sex partner).20 There is fair evidence to indicate that a broader strategy targeted to individuals who report risk factors, combined with routine (voluntary) testing of those being seen in high-prevalence clinical settings, would result in substantially fewer missed diagnoses.21-23 In 2 good-quality studies, HIV screening of populations with a 1-perecent prevalence rate was found to be cost-effective (in terms of acceptable cost per quality-adjusted life-year) compared with no screening.24,25 One study25 found that screening populations with even lower prevalence rates is also cost-effective if one assumes secondary transmission benefits. Neither study, however, reported on the incremental cost-effectiveness of screening lower-risk versus higher-risk patients.
The wide adoption in 1995 to 1997 of the use of HAART regimens with 3 or more antiretroviral agents has been associated with a marked decline in morbidity and mortality of HIV-infected patients in the United States.3 Good quality evidence has shown HAART regimens to be consistently effective in reducing clinical progression and mortality in persons with CD4 cell counts less than 200 cells/mm3;26,27 the percentage of patients found in studies to be candidates for HAART regimens at the time of HIV diagnosis has ranged from 12% to 43%.20,28 In addition, 2 good-quality systematic reviews found that the use of antibiotic medication to prevent opportunistic infections (e.g., Pneumocystis carinii pneumonia and disseminated Mycobacterium avium-intracellulare complex) is effective in persons with advanced disease.29,30 Theoretically, asymptomatic patients in an earlier stage of disease at the time of diagnosis (CD4 cell counts between 200-350 cells/mm3 or viral load >100,000 copies/mL) may also benefit from HAART regimens. However, there are no completed trials showing clinical benefit from treatment versus no treatment in such patients. Data from the Strategies for Management of Anti-Retroviral Therapy (SMART) trial, which focuses on this group, will not be available for a few more years.
The standard of care in the United States for preventing vertical HIV transmission in seropositive pregnant women has evolved from monotherapy (zidovudine) to combination antiretroviral regimens, including HAART regimens, starting at 14-34 weeks gestation through labor and augmented with 6 weeks of neonatal prophylaxis with zidovudine.31 Avoidance of breastfeeding is recommended for seropositive women since observational studies have shown that breastfeeding increases transmission rates even when adjusted for other factors, including antiretroviral use. A good-quality randomized clinical trial has demonstrated that elective cesarean section also reduces vertical transmission, compared with other modes of delivery, by minimizing contact between the fetus and infected maternal bodily fluids,32 although the benefit appears small in women with undetectable viral loads. There is fair to good evidence that the newer regimens, in combination with formula feeding and elective cesarean delivery, are associated with a reduction in perinatal transmission of 14 percent to 25 percent without interventions to 1 percent to 2 percent with interventions.
Information about the consequences of false-positive HIV test results (i.e., anxiety, labeling) is mostly anecdotal, although true-positive HIV test results have been shown to result in anxiety, depression, social stigmatization, changes in relationships with sexual partners, and discrimination.33 Evidence suggests that persons testing positive for HIV (especially heterosexual, serodiscordant couples) are more likely than others to avoid risky sexual behavior. On the other hand, optimistic beliefs about the effectiveness of HAART regimens have been shown to be associated with increased risky behaviors in individuals known to be seropositive.34,35 All antiretroviral drugs and drug combinations are associated with specific harm profiles, although most harms are short term or self limited and effective alternatives can often be found.36 Metabolic disturbances (hyperlipidemia and diabetes) related to HAART regimens have been associated with an increased incidence of cardiovascular events, especially with longer exposure.37 The estimated 3-year benefits of HAART regimens appear, however, to greatly outweigh the cardiovascular complications.
No significant increases in the rates of congenital anomalies, neonatal conditions, or other fetal harm have been associated with in utero exposure to FDA-approved regimens of antiretroviral drugs,38 with the exception of those including efavirenz. Efavirenz has recently been re-classified as Class D in pregnancy (positive evidence of human fetal risk). Although studies have demonstrated no ill effects of limited exposure to zidovudine monotherapy in women followed postpartum for as long as 6 years, no studies have evaluated the effects of limited exposure to combination antiretroviral drugs during pregnancy on the long-term clinical outcomes of HIV-infected women.
Counseling and HIV testing of high risk individuals (as defined in the Clinical Considerations section) are recommended by the CDC,39 the Canadian Task Force on the Periodic Health Examination (now the Canadian Task Force on Preventive Health Care)40, and numerous professional organizations, including the American Medical Association (AMA),41 the American Academy of Family Physicians (AAFP),42 the American College of Obstetricians and Gynecologists (ACOG),43 the American College of Physicians (ACP),44 and the Infectious Diseases Society of America (IDSA).45 Also, the American Academy of Pediatrics (AAP)46 considers all sexually active adolescents to be a high risk group and recommends they be counseled and offered HIV testing. In addition, the CDC recommends that routine, voluntary testing be offered to all patients seen either in health care facilities where the prevalence of HIV infection is 1 percent or greater or in settings serving client populations at increased behavioral or clinical HIV risk.
The CDC, AMA, AAFP, ACOG, IDSA, AAP,47 and the American College of Nurse-Midwives48 recommend that all pregnant women be routinely counseled and encouraged to have HIV testing. ACOG, AAP, and the CDC go further in recommending that HIV testing be part of a routine battery of prenatal blood tests unless declined (i.e., an "opt-out" approach). The CDC and ACOG also recommend retesting women in their third trimester of pregnancy who are known to be at high risk for acquiring HIV, as well as rapid HIV testing in labor for women with undocumented HIV status.
Members of the U.S. Preventive Services Task Force* are are Ned Calonge, M.D., M.P.H., Chair, USPSTF (Acting Chief Medical Officer and State Epidemiologist, Colorado Department of Public Health and Environment, Denver, CO); Janet D. Allan, Ph.D., R.N., C.S., Vice-chair, USPSTF (Dean, School of Nursing, University of Maryland, Baltimore, Baltimore, MD); Alfred O. Berg, M.D., M.P.H. (Professor and Chair, Department of Family Medicine, University of Washington, Seattle, WA); Paul S. Frame, M.D. (Family Physician, Tri-County Family Medicine, Cohocton, NY, and Clinical Professor of Family Medicine, University of Rochester, Rochester, NY); Joxel Garcia, M.D., M.B.A. (Deputy Director, Pan American Health Organization, Washington, DC); Russell Harris, M.D., M.P.H. (Professor of Medicine, Sheps Center for Health Services Research, University of North Carolina School of Medicine, Chapel Hill, NC); Mark S. Johnson, M.D., M.P.H. (Professor and Chair, Department of Family Medicine, University of Medicine and Dentistry of New Jersey-New Jersey Medical School, Newark, NJ); Jonathan D. Klein, M.D., M.P.H. (Associate Professor, Department of Pediatrics, University of Rochester School of Medicine, Rochester, NY); Carol Loveland-Cherry, Ph.D., R.N. (Executive Associate Dean, School of Nursing, University of Michigan, Ann Arbor, MI); Virginia A. Moyer, M.D., M.P.H. (Professor, Department of Pediatrics, University of Texas Health Science Center, Houston, TX); C. Tracy Orleans, Ph.D. (Senior Scientist, The Robert Wood Johnson Foundation, Princeton, NJ); Albert L. Siu, M.D., M.S.P.H. (Professor and Chairman, Brookdale Department of Geriatrics and Adult Development, Mount Sinai Medical Center, New York, NY); Steven M. Teutsch, M.D., M.P.H. (Executive Director, Outcomes Research and Management, Merck & Company, Inc., West Point, PA); Carolyn Westhoff, M.D., M.Sc. (Professor of Obstetrics and Gynecology and Professor of Public Health, Columbia University, New York, NY); and Steven H. Woolf, M.D., M.P.H. (Professor, Department of Family Practice and Department of Preventive and Community Medicine and Director of Research, Department of Family Practice, Virginia Commonwealth University, Fairfax, VA).
* Members of the Task Force at the time this recommendation was finalized. For a list of current Task Force members, go to http://www.uspreventiveservicestaskforce.org/about.htm.
This document is in the public domain within the United States. Requests for linking or to incorporate content in electronic resources should be sent via the USPSTF contact form.
Disclaimer: Recommendations made by the USPSTF are independent of the U.S. Government. They should not be construed as an official position of AHRQ or the U.S. Department of Health and Human Services.
Source: U.S. Preventive Services Task Force. Ann Intern Med 2005;143:32-37.
The complete information on which this statement is based, including evidence tables and references, is included in the summaries of evidence,49,50 evidence syntheses,51,52 and an April 2007 Evidence Update, available through the USPSTF Web site (https://www.uspreventiveservicestaskforce.org).
This recommendation is also posted on the Web site of the National Guideline Clearinghouse™ at: http://www.guideline.gov.
A previous version of this recommendation statement was first published in Ann Intern Med 2005;143:32-37.
2. Harris RP, Helfand M, Woolf SH, et al; Methods Work Group, Third U.S. Preventive Services Task Force. Current methods of the U.S. Preventive Services Task Force: a review of the process. Am J Prev Med 2001;20(3S):21-35.
3. Centers for Disease Control and Prevention. Cases of HIV Infection and Aids in the United States, 2002. HIV/AIDS Surveillance Report, Vol. 14. Accessed at /www.cdc.gov/hiv/stats/hasr1402.htm on 23 March, 2005.
4. Fleming P, Byers RH, Sweeney PA, Daniels D, Karon JM, Janssen RS. HIV prevalence in the United States, 2000. In: Program and abstracts of the 9th Conference on Retroviruses and Opportunistic Infections. Seattle, Washington; February 24-28, 2002. Alexandria, Virginia: Foundation for Retrovirology and Human Health.
9. Office of the Inspector General. Reducing obstetrician barriers to offering HIV testing. Washington, DC: Department of Health and Human Services; 2002. Accessed at www.aidscience.org/articles/aidscience017.asp on 12 March 2005.
14. O'Connell RJ, Merrit TM, Malia JA, et al. Performance of the OraQuick rapid antibody test for diagnosis of human immunodeficiency virus type 1 infection in patients with various levels of exposure to highly active antiretroviral therapy. J Clin Microbiol 2003;41(5);2153-5.
15. Reynolds SJ, Ndongala LM, Luo CC, et al. Evaluation of a rapid test for the detection of antibodies to human immunodeficiency virus type 1 and 2 in the setting of multiple transmitted viral subtypes. Int J STD AIDS 2002;13(3):171-3.
16. Gallo D, George JF, Fitchen JH, Goldstein AS, Hindahl MS. Evaluation of a system using oral mucosal transudate for HIV-1 antibody screening and confirmatory testing. OrasSure HIV Clinical Trials Group. JAMA 1997;277(3):254-8.
17. Martinez PM, Torres AR, de Lejarazu R, et al. Human immunodeficiency virus antibody testing by enzyme-linked fluorescent and Western blot assays using serum, gingival-crevicular transudate, and urine samples. J Clin Microbiol 1999;37:1100-6.
20. Klein D, Hurley LB, Merrill D, Quescenberry CP, Jr. Review of medical encounters in the 5 years before a diagnosis of HIV-1 infection: implications for early detection. J Acquir Immune Defic Syndr 2003;32:143-52.
26. McNaghten AD, Hanson DL, Jones JL, Dworkin MS, Ward JW. Effects of antiretroviral therapy and opportunistic illness primary chemoprophylaxis on survival after AIDS diagnosis. Adult/Adolescent Spectrum of Disease Group. AIDS 1999;13(13):1687-95.
28. Dybul M, Bolan R, Condoluci D, et al. Evaluation of initial CD4+ T cell counts in individuals with newly diagnoses human immunodeficiency virus infection, by sex and race, in urban settings. J Infect Dis 2002;185:1818-21.
30. Bucher HC, Griffith L, Guyatt GH, Opravil M. Meta-analysis of prophylactic treatments against Pneumocystic carinii pneumonia and toxoplasma encephalitis in HIV-infected patients. J Acquir Immune Defic Syndr Hum Retrovirol 1997;15(2):104-14.
31. Centers for Disease Control and Prevention. Recommendations for use of antiretroviral drugs in pregnant HIV-1 infected women for maternal health and interventions to reduce perinatal HIV-1 transmission in the United States. Accessed at http://aidsinfo.nih.gov/guidelines/perinatal/PER_062304.pdf on 23 March, 2005.
32. The European Mode of Delivery Collaboration. Elective caesarean-section versus vaginal delivery in prevention of vertical HIV-1 transmission: a randomised clinical trial. Lancet 1999;353(9158):1035-9.
34. Centers for Disease Control and Prevention. Adoption of protective behaviors among persons with recent HIV infection and diagnosis—Alabama, New Jersey, and Tennessee, 1997-1998. MMWR Morb Mortal Wkly Rep 2000;49:512-5.
39. Centers for Disease Control and Prevention. Revised guidelines for HIV counseling, testing, and referral and revised recommendations for HIV screening of pregnant women. MMWR Morb Mortal Wkly Rep 2001;50(19):1-86.
45. Aberg JA, Gallant JE, Anderson J, et al. Primary care guidelines for the management of persons infected with human immunodeficiency virus: recommendations of the HIV Medicine Association of the Infectious Diseases Society of America. Clin Infect Dis 2004;39(5):609-29.
48. American College of Nurse-Midwives. Position statement: Human Immunodeficiency Virus (HIV) and Acquired Immunodeficiency Syndrome (AIDS). 2003. Accessed at www.midwife.org/prof/display.cfm?id=403 on 24 March, 2005.
50. Chou R, Smits AK, Huffman LH, Fu R, Korthuis PT. Prenatal screening for human immunodeficiency virus: a review of the evidence for the U.S. Preventive Services Task Force. Ann Intern Med 2005;143:38-54.
51. Chou R, Korthuis PT, Huffman LH, Smits AK. Screening for Human Immunodeficiency Virus in Adolescents and Adults. Evidence Synthesis No. 38. (Prepared by the Oregon Evidence-based Practice Center under Contract No. 290-02-0024). Rockville, MD: Agency for Healthcare Research and Quality. July 2005.
52. Chou R, Smits AK, Huffman LH, Korthuis PT. Screening for Human Immunodeficiency Virus in Pregnant Women. Evidence Synthesis No. 39. (Prepared by the Oregon Evidence-based Practice Center under Contract No. 290-02-0024). Rockville, MD: Agency for Healthcare Research and Quality. July 2005. http://www.ncbi.nlm.nih.gov/books/NBK33383/. Accessed May 20, 2019.