Initial and Interim Laboratory and Other Tests

• For HIV staging and prognosis
• Helps guide initiation of ART
• Indicates risk of opportunistic illnesses and guides initiation of prophylaxis against opportunistic infections
• Used to monitor immune reconstitution during ART

• Reported in cells/µL

• Perform at baseline (twice).
• Repeat every 3-6 months for stable patients on or off ART.
• Repeat if results are inconsistent with the clinical picture or with previous trends.
• See chapter CD4 and Viral Load Monitoring.

• Used in addition to the absolute CD4 count for monitoring trends; may be discrepant with absolute CD4
• Pneumocystis pneumonia prophylaxis is indicated for CD4 percentage <14% regardless of absolute count

• Usually obtained with absolute CD4 count.

• Estimates level of HIV replication
• Used to monitor effect of ART
• May be used to identify acute HIV infection; has high sensitivity in setting of acute infection, when antibody may be negative; must be confirmed by positive result on HIV antibody test (one viral load test is FDA approved for diagnosis of HIV)

• Reported in copies/mL
• In untreated patients, detectable (with rare exceptions) and measured to the upper limit of detection (usually >500,000 copies/mL)
• For patients taking ART, ideally suppressed to undetectable levels (usually <50 or <75 copies/mL)

• Perform at baseline (twice).
• For patients on new or modified ART regimen: perform 2-8 weeks after initiation or change in ART, then every 4-8 weeks until viral load is suppressed.
• For patients on stable ART: perform every 3-4 months (if stable and viral load suppressed >2-3 years, consider every 6 months).
• For patients not taking ART: perform every 3-6 months; more frequently if CD4 count is low.

Factors that may temporarily increase viral load:

• Immunizations
• Active infections

• To assess whether the patient's HIV virus is likely to be resistant to specific ARV medications

• Genotype: detects specific mutations to ARV medications
• Phenotype: measures HIV viral replication in the presence of ARVs

• Genotype is recommended for all ARV-naive patients. For greatest accuracy, should be done as early as possible in the course of HIV infection.
• Acute or primary infection: recommended (genotype).
• Chronic infection and treatment naive: recommended before initiation of ART (genotype). If resistance test was performed at entry, consider repeat testing.
• Pregnancy: recommended before initiation of ART or for patients with detectable HIV RNA while taking ART.
• Virologic failure: recommended.
• Consider genotype for integrase mutations if integrase inhibitor resistance is a concern.

• Determine coreceptor tropism

• If CXCR4-tropic (or dual/mixed tropic) virus is detected, CCR5 antagonist is not likely to be effective and should be avoided

• Test before making decision to treat with CCR5 antagonist, or if virologic failure occurs while on a CCR5 antagonist.
• For standard assay, HIV RNA must be >1,000 copies/mL (a proviral DNA test is available for samples with HIV RNA below limits of detection; has not been clinically validated).

• Establish risk of hypersensitivity reaction to abacavir

• If positive, high risk of abacavir hypersensitivity reaction; abacavir should not be used

• Test before starting treatment with abacavir.

• Detects anemia, thrombocytopenia, leukopenia

• Normal

• Perform at baseline.
• Repeat every 3-6 months.

• Abnormal

• Requires follow-up evaluation as indicated; may influence choice of ARVs.
• Repeat more frequently if the patient's results are abnormal or if the patient is taking bone marrow suppressive drugs.

• Detects electrolyte abnormalities, kidney disease, liver disease

• Normal/abnormal

• Perform at baseline; before starting ART.
• Repeat every 3-6 months, and as needed.
• May influence ARV selection.
• May be useful in monitoring drug toxicities.
• Abnormalities should prompt evaluation of cause.

• Used to screen for kidney disease

• Normal/abnormal

• Screen at baseline and before initiation or change of ART regimen.
• Repeat every 6 months in patients with HIV-associated nephropathy.
• Repeat every 12 months (for patients on tenofovir, every 6 months); more frequently if indicated.
• Abnormalities should prompt evaluation of cause.

• Detects dyslipidemia, identifies risk factors for cardiovascular disease

• Normal/abnormal

• Baseline; before starting ART.
• Repeat ≤3 months after starting or changing ART, annually if normal (on or off ART), or more frequently (every 3-6 months) if abnormal or risk of cardiovascular disease.
• May influence ARV selection.
• May be useful in monitoring drug toxicities.

See chapter Dyslipidemia.

• Detects diabetes and hyperglycemia

• Normal/abnormal Baseline

• Repeat every 3 months if abnormal, every 6 months if normal.
• May influence ARV selection.
• May be useful in monitoring drug toxicities.

• Screen for immunity to hepatitis A; vaccinate those not immune

• Negative

• Offer hepatitis A vaccine if indicated. (See chapter Immunizations for HIV-Infected Adults and Adolescents.)

• Positive

• Immune; no vaccine necessary.

• Indicates active hepatitis B

• sAg negative

• Most likely, no chronic infection (may be falsely negative).
• Vaccinate if HBsAb negative (not immune).

• sAg positive

• Indicates chronic or acute hepatitis B infection; requires further evaluation (check HBV DNA). (See chapter Hepatitis B Infection.)

• Indicates past infection or ongoing infection

• Anti-HBc negative

• The patient most likely has not been infected with hepatitis B; consider vaccination if HBsAb negative and HBsAg negative.

• Anti-HBc positive

• The patient most likely has been infected with hepatitis B; this test alone does not distinguish past exposure and active infection.
• In rare cases, may be falsely negative in some patients with chronic infection.
• If sAb negative and sAg negative, check HBV DNA to rule out active infection.
• If sAb is positive, patient is immune.

• Indicates immunity status

• Anti-HBs negative

• The patient is not immune to hepatitis B; consider vaccination, unless patient has active hepatitis (sAg positive or HBV DNA positive).

• Anti-HBs positive

• The patient is immune to hepatitis B either by previous infection or by immunization; may be negative in acute hepatitis B infection.

• Hepatitis C status

• HCV negative

• Patient is not infected with hepatitis C.
• Consider annual screening for high-risk patients.

• HCV positive

• Patient has chronic hepatitis C infection or past infection with spontaneous clearance (no protective immunity); confirm positive results with HCV RNA.

• Detects past exposure; if positive, patient has increased risk of developing CNS toxoplasmosis if CD4 count <100 cells/µL

• Negative

• Repeat if patient becomes symptomatic or when CD4 count drops to ≤100 cells/µL.

• Positive

• Note as baseline information.
• Start toxoplasmosis prophylaxis when CD4 count drops to ≤100 cells/µL.

• Detects latent TB infection (LTBI)

• Normal

• Repeat every 6-12 months.
• Repeat TST if CD4 count was <200 cells/µL on initial TST but increases to >200 cells/µL.

• Abnormal (TST induration ≥5 mm or positive IGRA)

• Evaluate for active TB. (See chapter Latent Tuberculosis.)

• Detects latent or active diseases

• Normal

• Repeat as indicated for pulmonary symptoms or positive LTBI test.

• Abnormal

• Evaluate for TB, PCP, or other pathology.

• Detects abnormal cell changes, dysplasia

• Normal

• Cervical: Repeat in 6 months; then annually if negative on two tests and no ongoing risk factors.
• Anal: Follow-up interval has not been determined; consider same as in cervical Pap screening.

• Abnormal

• Perform workup, treat (see chapters Cervical Dysplasia and Anal Dysplasia) and follow up more frequently as indicated by condition.

• Indicates pregnancy status

• Positive/negative

• Perform before starting efavirenz (given risk for teratogenicity).
• If positive, consider ART initiation; avoid efavirenz (see chapters Reducing Maternal-Infant HIV Transmission and Care of HIV-Infected Pregnant Women).

• Syphilis screening

• Negative/nonreactive

• Repeat every 3-12 months, depending on risk factors.

• Positive/reactive: confirm with treponemal test

• Treat patient; refer partner(s) of previous 60 days for evaluation and treatment; counsel about safer sex.
• Perform serial testing if monitoring active disease. (See chapter Syphilis.)

• Pharynx (recommended for GC screening)
• Cervix/vagina
• Urethra
• Rectum

• Negative

• Counsel about safer sex and avoiding STIs.
• Repeat every 6-12 months; more frequently if at high risk.

• Positive

• Treat patient; refer partner(s) of previous 60 days for evaluation and treatment; counsel about safer sex.

• Wet mount or culture of vaginal secretions

• Negative

• Counsel about safer sex and avoiding STIs.

• Positive

• Treat patient; refer partner(s) for evaluation and treatment; counsel about safer sex.

• Screen for STIs in sexually active men who are at risk, especially men who have sex with men (MSM)
• Screen all at baseline; frequency of subsequent testing depends on risk factors
• Screen sites of possible exposures:
  • Pharynx (recommended for GC screening)
  • Rectum
  • Urethra (consider for MSM with history of unprotected insertive intercourse in preceding year)

• Negative

• Retest every 3-6 months for patients with risk factors.

• Positive

• Treat; refer partner(s) of previous 60 days for evaluation and treatment; counsel about safer sex.

• Prevent hemolytic reactions to certain medications by screening higher-risk patients (African, Mediterranean, Asian, Sephardic Jewish descent); some would recommend screening all patients

• Normal range

• No intervention is necessary beyond documentation.

• Abnormal range

• Avoid oxidant drugs such as dapsone, primaquine, and sulfonamides, if possible.

• Detects exposure; may reveal future disease risk

• Negative

• Avoid exposure by practicing safer sex.
• If blood transfusion is required, use CMV-negative or leukocyte-reduced blood.

• Positive

• Be aware of disease risk in advanced HIV infection, when CD4 count is <50 cells/µL.

• Detects exposure

• Negative

• Consider vaccination, if CD4 count is >200 cells/µL.

• Positive

• No intervention is necessary.

• Detects CMV, ophthalmic toxoplasmosis, or HIV retinopathy

• Normal

• If CD4 count is >100 cells/µL, repeat annually.
• If CD4 count is <50 cells/µL or symptoms of retinal changes are present, repeat every 6 months.

• Abnormal

• Follow up immediately with ophthalmologist.