Tests
1st tests to order
maternal HIV-1/HIV-2 antigen/antibody enzyme-linked immunosorbent assay (ELISA)
Test
All HIV-negative pregnant women should be tested as early as possible during each pregnancy. Partners of pregnant women should also be encouraged to undergo testing if their HIV status is unknown.[7]
The need for repeat testing depends on the testing modality used and its window period. Repeat testing is recommended in the third trimester (before 36 weeks’ gestation) in patients with an initial negative test during pregnancy who: are at high risk of acquiring HIV; who are receiving health care in facilities that have an HIV incidence of at least 1 case per 1000 pregnant women per year or reside in jurisdictions with elevated HIV incidence in females ages 14-45 years; reside in states that require third-trimester testing; have signs or symptoms of acute infection. Repeat testing should also be considered at points in the pregnancy when clinically indicated (e.g., symptoms suggestive of a sexually transmitted infection, ongoing exposure to HIV). Testing should also be offered to pregnant women who perceive themselves to be at increased risk for HIV infection (regardless of whether or not they fit any of the above criteria).[7][73]
Expedited HIV testing (i.e., testing performed in situations when a very short turnaround time is optimal) should be performed during labor (or after delivery) in women with undocumented HIV status, and those who tested negative early in pregnancy but have increased exposure to HIV and were not retested in the third trimester. Women who have not been tested either before or during labor should undergo expedited testing in the immediate postpartum period.[7]
Initial test should be the fourth-generation antigen/antibody combination ELISA that detects HIV-1 and HIV-2 antibodies and HIV-1 p24 antigen. The assay is used to screen for established infection with HIV-1 or HIV-2 and for acute HIV-1 infection.[7][71]
Rapid tests may be used for initial testing in some clinical settings. These tests may detect a combination of antigen and antibodies, or antibodies only. A positive result on a rapid test should be followed by laboratory-based testing for confirmation.[7]
Patients with a reactive immunoassay should be tested further with an HIV-1/HIV-2 antibody differentiation assay.[7] No further testing is required for specimens that are nonreactive on the initial immunoassay.
Result
positive
maternal HIV-1/HIV-2 antibody differentiation immunoassay
Test
If the antigen/antibody combination immunoassay result is reactive, the specimen should be tested with an antibody immunoassay that differentiates HIV-1 antibodies from HIV-2 antibodies.[7]
Enzyme-linked immunosorbent assay (ELISA) is preferred, but western blot or indirect immunofluorescence assay may also be used if ELISA is not available.[71]
Patients with a reactive antigen/antibody immunoassay, and a nonreactive differentiation test, should be tested with an HIV RNA assay to assess for acute HIV infection.[7]
Result
positive for HIV-1 antibodies; or positive for HIV-2 antibodies; or positive for HIV antibodies, undifferentiated
neonatal HIV DNA or RNA polymerase chain reaction (PCR)
Test
HIV-exposed infants should be tested for HIV infection. Testing is recommended in all infants with perinatal HIV exposure at 14-21 days; 1-2 months; and 4-6 months. Testing at birth should be considered in infants at high risk of infection (and 2-6 weeks after cessation of antiretroviral prophylaxis). A positive result should be confirmed by repeat testing on a second specimen as soon as possible.[7]
For infants with perinatal exposure who are being breast-fed, testing should be considered at birth, 14-21 days, 1-2 months, and 4-6 months of age, with an additional test performed between the 1-to-2-month and 4-to-6-month tests if the gap between the tests is more than 3 months. Testing should be performed every 3 months during breast-feeding, and 4-6 weeks, 3 months, and 6 months after breast-feeding has ceased.[7]
HIV can be excluded in infants who have not been breast-fed with 2 or more negative tests (either 1 test obtained at ≥1 month of age and 1 at ≥4 months of age, or 2 tests from separate specimens at ≥6 months of age). Additional testing is generally not needed after this, but infants with potential exposure after birth require additional testing (i.e., virologic testing for those <18 months, and HIV antigen/antibody testing for those ≥18 months). Age-appropropriate testing is also recommended for infants and children with signs and symptoms of HIV, even in the absence of exposure.[7]
In the case that a mother without a known diagnosis of HIV tests positive for HIV during labor, delivery, or postpartum, HIV RNA testing is recommended for the infant as early as possible. If maternal HIV test results are not available at birth, the infant should be tested using an expedited antibody test to identify perinatal exposure, and if the result of the infant’s test is positive an HIV RNA assay should be performed on the infant.[7]
Sensitivity of DNA and RNA PCR testing is high and increases rapidly after 2 weeks of age.[78] Sensitivity and specificity of point-of-care molecular testing was high (98.6% and 99.99%, respectively) in children <18 months of age who were exposed to HIV.[79]
Result
positive
Tests to consider
HIV-1 western blot
Test
HIV-1 western blot may be used as a second-line alternative to HIV-1/HIV-2 antibody differentiation immunoassay.[71]
If test results are negative or indeterminate, HIV-1 nucleic acid test should be performed.
Result
positive for HIV-1 antibodies
HIV-1 indirect immunofluorescence assay (IFA)
Test
HIV-1 IFA may be used instead of an HIV-1/HIV-2 antibody differentiation immunoassay.[71]
If test results are negative or indeterminate, HIV-1 nucleic acid test should be performed.
Result
positive for HIV-1 antibodies
HIV-1 nucleic acid test (NAT)
Test
If the HIV-1/HIV-2 antigen/antibody combination immunoassay result is reactive and HIV-1/HIV-2 antibody differentiation immunoassay is nonreactive or indeterminate, the specimen should be tested with an HIV-1 NAT.[71]
A reactive HIV-1 NAT and a nonreactive HIV-1/HIV-2 antibody differentiation immunoassay indicates laboratory evidence for acute HIV-1 infection.
A reactive HIV-1 NAT and an indeterminate HIV-1/HIV-2 antibody differentiation immunoassay indicates the presence of HIV-1 infection confirmed by HIV-1 NAT.
A negative HIV-1 NAT and a nonreactive or indeterminate HIV-1/HIV-2 antibody differentiation immunoassay result indicates a false-positive result on the initial combination immunoassay.
Result
positive
CD4 count
Test
Indicates immune status and assists in the staging process.
Should be performed at the initial visit in all women, with a review of prior CD4 counts. It should be repeated at least every 3 months during pregnancy in women who have been on treatment for <2 years, patients with CD4 counts <300 cells/microliter, and those with inconsistent adherence and/or detectable viral loads. Women who have been on treatment for ≥2 years and who have had consistent viral suppression and CD4 counts ≥300 cells/microliter do not require further monitoring during pregnancy. Women who have been on ART for <2 years with CD4 counts ≥300 cells/microliter should be monitored every 6 months.[7]
Do not test for other more complex lymphocyte panels (such as CD8 count or CD4/CD8 ratio), as they add cost without offering clinical benefit.[74]
Result
CD4 count >500 cells/microliter: patients are usually asymptomatic; CD4 count <350 cells/microliter: implies substantial immune suppression; CD4 count <200 cells/microliter: places the patient at risk for most opportunistic infections
plasma HIV RNA levels (viral load)
Test
It is standard to obtain serial viral loads in pregnant women who test positive for HIV.
Should be monitored at the initial visit in all women (with a review of prior HIV RNA levels), 2-4 weeks after initiating or changing drug treatment, monthly until HIV RNA levels are undetectable, and then at least every 3 months during pregnancy. Should also be assessed at 36 weeks’ gestation (or within 4 weeks of delivery) to inform decisions about mode of delivery.[7]
Result
recently infected patients or patients in late stages of infection may have levels in the region of millions of copies/mL
renal function tests
Test
Performed at baseline, initiation or modification of antiretroviral therapy, and monitored regularly during treatment or as needed for other clinical care.
Result
may indicate impaired renal function
liver function tests (LFTs)
Test
Performed at baseline, initiation or modification of antiretroviral therapy (ideally within 2-4 weeks), and every 3 months during pregnancy or as needed for other clinical care.[7]
Result
may be normal; baseline abnormal LFTs may reflect chronic hepatitis B, chronic hepatitis C, or alcoholism
drug resistance tests
Test
Perform before: initiating antiretroviral therapy (ART) in treatment-naive pregnant women who have not previously been tested for resistance; initiating ART in treatment-experienced pregnant women (including those who have received pre-exposure prophylaxis); modifying ART regimens in those who are newly pregnant and receiving treatment or who have suboptimal virologic response to ART initiated during pregnancy.[7]
Should be performed in all pregnant women with virologic failure whose HIV RNA levels are >200 copies/mL. Testing may be unsuccessful in people with <500 copies/mL but should still be considered.[7]
Treatment should be initiated prior to receiving results as the regimen can be modified once they are obtained. Phenotypic resistance testing is indicated for treatment-experienced people on failing regimens who are thought to have multidrug resistance.[7]
Aids in choice of the most appropriate treatment regimen.
Result
variable
complete blood count
Test
Performed at baseline, initiation or modification of antiretroviral therapy, and monitored regularly during treatment or as needed for other clinical care.
Result
may be normal or show anemia or thrombocytopenia
glucose screening
Test
Standard gestational diabetes screening is recommended for women on antiretroviral therapy. Some experts may perform glucose screening earlier in pregnancy for patients who are on protease inhibitors and who may be at high risk for gestational diabetes.[7]
Result
variable
fetal ultrasound
Test
Women should have an ultrasound as soon as possible to confirm gestational age. Ultrasound is also recommended for anatomical survey during the second trimester.[7]
Result
confirms gestational age; may show anatomical abnormalities
tests for coinfections
Test
Screening for tuberculosis, viral hepatitis, and sexually transmitted infections should be done early in every pregnancy.
Result
may be positive
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