Interferon gamma release assays (IGRAs), such as the QuantiFERON-TB Gold assay, detect circulating T cells reactive with antigens of Mycobacterium tuberculosis (M.tb). The tuberculin skin test (TST) also detects M. tuberculosis-reactive T cells but T cells reactive with antigens of BCG and non-tuberculous mycobacteria may also be detected, resulting in a higher rate of false positive tests for M.tb infection. Although IGRA results do not always concur with TST results, there are several practical advantages to using IGRAs rather than TSTs. In people with HIV infection, a positive IGRA can indicate either latent tuberculosis (TB) or, less commonly, active TB. A negative result, however, does not exclude active TB as there is a significant rate of false negative results in active TB infection, and other testing strategies (Mycobacterial culture, PCR) should be pursued in symptomatic patients.
IGRAs are recommended for patients who have been exposed to people with TB or are from a country with a high prevalence or have travelled to a region of high prevalence of TB.
A baseline chest x-ray is recommended for all newly diagnosed HIV patients with a CD4+ T cell count of <200/µL, report symptoms suggestive of respiratory tract disease, or have been exposed to people who have TB or are from a country with a high prevalence of TB.
Long-acting cabotegravir as pre-exposure prophylaxis (PrEP) was TGA approved in August 2022 but is not reimbursed under the PBS or commonly used as PrEP in Australia.
Overseas travellers or Australians returning from overseas may have accessed long-acting cabotegravir as PrEP. To exclude integrase strand transfer inhibitor (INSTI) resistance, providers should ensure that genotypic resistance testing also includes the integrase gene (AIII).
Laboratory Testing for Initial Assessment and Monitoring of People with HIV Receiving Antiretroviral Therapy
Several laboratory tests are important for initial evaluation of people with HIV upon entry into care. Some tests should be performed before and after initiation or modification of antiretroviral therapy (ART) to assess the virologic and immunologic efficacy of ART and to monitor for laboratory abnormalities that may be associated with antiretroviral (ARV) drugs. Table 3 below outlines recommendations from the Panel on Antiretroviral Guidelines for Adults and Adolescents on the frequency of testing. As noted in the table, some tests may be repeated more frequently if clinically indicated. Two surrogate markers are used to monitor people with HIV: plasma HIV RNA (viral load) to assess level of HIV viremia and CD4+ T lymphocyte cell count (or CD4 count) to assess immune function. Standard (reverse transcriptase and protease) genotypic drug-resistance testing should be used to guide selection of an ARV regimen; if transmitted integrase strand transfer inhibitor (INSTI) resistance is a concern or for people who acquired HIV after taking long-acting cabotegravir as pre-exposure prophylaxis, testing also should include the integrase gene (see Drug-Resistance Testing). For guidance on the choice of ARV regimens before drug-resistance testing results become available, clinicians should consult the What to Start section. A viral tropism assay should be performed before initiation of a CCR5 antagonist or at the time of virologic failure that occurs while a patient is receiving a CCR5 antagonist. HLA-B*5701 testing should be performed before initiation of abacavir (ABC) to reduce the risk of hypersensitivity reaction, and HLA-B*5701-positive patients should not be prescribed ABC. Patients should be screened for hepatitis B and hepatitis C virus infections before initiating ART and, if indicated, periodically after ART initiation, because treatment of these coinfections may affect the choice of ART and likelihood of drug-induced hepatotoxicity. The rationale for and utility of some of these laboratory tests are discussed in the corresponding sections of the guidelines.Table 3. Laboratory Testing Schedule for Monitoring People with HIV Before and After Initiation of Antiretroviral Therapya
Laboratory Test | Timepoint or Frequency of Testing |
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Entry Into Care | ART Initiationb or Modification | 4 to 8 Weeks After ART Initiation or Modification | Every 3 Months | Every 6 Months | Every 12 Months | Treatment Failure | Clinically Indicated | If ART Initiation Is Delayedc |
|
HIV Antigen/ Antibody Test | √ If HIV diagnosis has not been confirmed | ||||||||
| CD4 Count | √ | √ | √d If CD4 count is <300 cells/mm3 | √ During the first 2 years of ART, if CD4 count is ≥ 300 cells/mm3 | √ After 2 Years on ART with Consistently Suppressed Viral Load CD4 Count 300–500 cells/mm3
| √ | √ | √ Every 3–6 months |
|
| HIV Viral Load | √ | √ | √e | √f | √f | √ | √ | Repeat testing is optional. |
|
| Genotypic Resistance Testing (PR/RT Genes)g | √ | √ | √ | √ | √ |
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| Genotypic Resistance Testing (Integrase Genes)g | √ If transmitted INSTI resistance is suspected or if there is a history of CAB-LA use for PrEP | √f If transmitted INSTI resistance is suspected or if there is a history of INSTI use | √ If there is a history of INSTI use | √ If there is a history of INSTI use | |||||
| Tropism Testing | √ If considering a CCR5 antagonist | √ If considering a CCR5 antagonist, or for patients with virologic failure on a CCR5 antagonist | √ | ||||||
| HLA-B*5701 Testing | √ If considering ABC | ||||||||
Hepatitis B Serology (HBsAb, HBsAg, HBcAb total)h,i,j | √ | In patients not immune to HBV, consider retesting if switching to a regimen that does not contain TDF or TAF. | √ Including before starting HCV DAA | ||||||
Hepatitis C Screening (HCV antibody or, if indicated, HCV RNA)k | √ | √ Repeat HCV screening for at-risk patientsl | √ | ||||||
Basic Metabolic Panelm,n | √ | √ | √ | √ | √ | √ Every 6–12 months |
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| ALT, AST, Total Bilirubin | √ | √ | √ | √ | √ | √ Every 6–12 months |
|||
| CBC with Differentialo | √ | √ | √ When monitoring CD4 count (if required by lab) | √ When monitoring CD4 count (if required by lab) | √ When no longer monitoring CD4 count | √ | |||
| Lipid Profilep | √ | Consider 1–3 months after ARV initiation or modification | √ If normal at baseline but with CV risk | If normal at baseline, every 5 years or if clinically indicated | |||||
| Random or Fasting Glucoseq | √ | √ | √ | √ | |||||
| Urinalysisn,r | √ | √ E.g., in patients with CKD or DM | |||||||
| Pregnancy Tests | √ | √ | √ | ||||||
| a This table pertains to laboratory tests done to select an ARV regimen and monitor for treatment responses or ART toxicities. Please refer to the HIV Medicine Association of the Infectious Diseases Society of America’s (HIVMA/IDSA) Primary Care Guidance for Persons with HIV for other laboratory tests generally recommended for primary health care maintenance of HIV patients.1 b If ART is initiated soon after HIV diagnosis and entry into care, repeat baseline laboratory testing is not necessary. c ART is indicated for all people with HIV and should be started as soon as possible. However, if ART initiation is delayed, patients should be retained in care, with periodic monitoring as noted above. d After 2 years of consistently suppressed HIV RNA, less frequent monitoring (e.g., every 6 months) may be considered. e If HIV RNA is detectable at 4–8 weeks, repeat testing every 4–8 weeks until viral load is suppressed to <50 copies/mL. Thereafter, repeat testing every 3–6 months. f For patients on ART, viral load typically is measured every 3–6 months. More frequent monitoring may be considered in individuals having difficulties with ART adherence or at risk for nonadherence. However, for adherent patients with consistently suppressed viral load and stable immunologic status for more than 1 year, monitoring can be extended to 6-month intervals. g Standard genotypic drug-resistance testing in ARV-naive persons should focus on testing for mutations in the PR and RT genes. If transmitted INSTI resistance is a concern, or if a person has a history of INSTI use as PrEP or treatment, or a person presents with viremia while on an INSTI, providers also should test for resistance mutations in the IN gene. In ARV-naive patients who do not immediately begin ART, repeat testing before initiation of ART is optional if drug-resistance testing was performed at entry into care. In patients with virologic suppression who are switching therapy because of toxicity or for convenience, viral amplification will not be possible; see the Drug-Resistance Testing section for a discussion of the potential limitations and benefits of proviral DNA assays in this situation. Results from prior drug-resistance testing should be considered because they can be helpful in constructing a new regimen. h If a patient has HBV infection (as determined by a positive HBsAg or HBV DNA test result), TDF or TAF plus either FTC or 3TC should be used as part of the ARV regimen to treat both HBV and HIV infections (see the Hepatitis B Virus/HIV Coinfection section). i If HBsAg, HBsAb, and HBcAb test results are negative, HBV vaccine series should be administered. Refer to the HIVMA/IDSA’s Primary Care Guidance for Persons with HIV and the Adult and Adolescent Opportunistic Infection Guidelines for detailed recommendations.1,2 j Most patients with isolated HBcAb have resolved HBV infection with loss of HBsAb. Consider performing an HBV viral load test for confirmation. If the HBV viral load test is positive, the patient may be acutely infected (and will usually display other signs of acute hepatitis) or chronically infected. If the test is negative, the patient should be vaccinated. Refer to the HIVMA/IDSA’s Primary Care Guidance for Persons with HIV and the Adult and Adolescent Opportunistic Infection Guidelines for more detailed recommendations.2 k The HCV antibody test may not be adequate for screening in the setting of recent HCV infection (acquisition within the past 6 months) or advanced immunodeficiency (CD4 count <100 cells/mm3). HCV RNA screening is indicated in persons who have been successfully treated for HCV or who spontaneously cleared prior infection. HCV antibody-negative patients with elevated ALT may need HCV RNA testing. l Injection drug users, people with a history of incarceration, men with HIV who have unprotected sex with men, and people with percutaneous/parenteral exposure to blood in unregulated settings are at risk of HCV infection. m Serum Na, K, HCO3, Cl, BUN, creatinine, glucose, and Cr-based eGFR. Serum P should be monitored in patients with CKD who are on TDF-containing regimens.3 n Consult the HIVMA/IDSA’s Clinical Practice Guideline for the Management of Chronic Kidney Disease in Patients Infected with HIV for recommendations on managing patients with renal disease.3 More frequent monitoring may be indicated for patients with evidence of kidney disease (e.g., proteinuria, decreased glomerular dysfunction) or increased risk of renal insufficiency (e.g., patients with diabetes, hypertension). o CBC with differential should be done when a CD4 count is performed. When CD4 count is no longer being monitored, the recommended frequency of CBC with differential is once a year. More frequent monitoring may be indicated for people receiving medications that potentially cause cytopenia (e.g., TMP-SMX). p If random lipids are abnormal, fasting lipids should be obtained. Consult the American College of Cardiology/American Heart Association’s 2018 Guideline on the Management of Blood Cholesterol for diagnosis and management of patients with dyslipidemia.4 q If random glucose is abnormal, fasting glucose should be obtained. HbA1C is no longer recommended for diagnosis of diabetes in people with HIV on ART (see the American Diabetes Association Guidelines).5 r Urine glucose and protein should be assessed before initiating TAF- or TDF-containing regimens and monitored during treatment with these regimens. s For persons of childbearing potential. Key: 3TC = lamivudine; ABC = abacavir; ALT = alanine aminotransferase; ART = antiretroviral therapy; ARV = antiretroviral; AST = aspartate aminotransferase; BUN = blood urea nitrogen; CAB-LA = cabotegravir long-acting; CBC = complete blood count; CD4 = CD4 T lymphocyte; CKD = chronic kidney disease; Cl = chloride; Cr = creatinine; CV = cardiovascular; DAA = direct-acting antiviral; DM = diabetes mellitus; eGFR = estimated glomerular filtration rate; FTC = emtricitabine; HbA1C = hemoglobin A1c; HBcAb = hepatitis B core antibody; HBsAb = hepatitis B surface antibody; HBsAg = hepatitis B surface antigen; HBV = hepatitis B virus; HCO3 = bicarbonate; HCV = hepatitis C virus; IN = integrase; INSTI = integrase strand transfer inhibitor; K = potassium; Na = sodium; P = phosphorus; PR = protease; PrEP = pre-exposure prophylaxis; RT = reverse transcriptase; TAF = tenofovir alafenamide; TDF = tenofovir disoproxil fumarate; TMP-SMX = trimethoprim-sulfamethoxazole |
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References
- Thompson MA, Horberg MA, Agwu AL, et al. Primary care guidance for persons with human immunodeficiency virus: 2020 update by the HIV Medicine Association of the Infectious Diseases Society of America. Clin Infect Dis. 2021;73(11):e3572-e3605. Available at: https://pubmed.ncbi.nlm.nih.gov/33225349.
- Panel on Guidelines for the Prevention and Treatment of Opportunistic Infections in Adults and Adolescents with HIV. Guidelines for the prevention and treatment of opportunistic infections in adults and adolescents with HIV. 2022. Available at: https://clinicalinfo.hiv.gov/en/guidelines/hiv-clinical-guidelines-adult-and-adolescent-opportunistic-infections/whats-new.
- Lucas GM, Ross MJ, Stock PG, et al. Clinical practice guideline for the management of chronic kidney disease in patients infected with HIV: 2014 update by the HIV Medicine Association of the Infectious Diseases Society of America. Clin Infect Dis. 2014;59(9):e96-138. Available at: http://www.ncbi.nlm.nih.gov/pubmed/25234519.
- Grundy SM, Stone NJ, Bailey AL, et al. 2018 AHA/ACC/AACVPR/AAPA/ABC/ACPM/ADA/AGS/APhA/ASPC/NLA/PCNA guideline on the management of blood cholesterol: a report of the American College of Cardiology/American Heart Association task force on clinical practice guidelines. Circulation. 2019;139(25):e1082-e1143. Available at: https://www.ncbi.nlm.nih.gov/pubmed/30586774.
- American Diabetes Association. Classification and diagnosis of diabetes: standards of medical care in diabetes-2019. Diabetes Care. 2019;42(Suppl 1):S13-S28. Available at: https://www.ncbi.nlm.nih.gov/pubmed/30559228.
