AIDS (HIV): Lab Test

1st order laboratory parameters – obligatory laboratory tests.

  • Current HIV screening test (Ag-Ak combination test) [diagnostic gap: 6 weeks].
    • HIV 1-p24 antigen [if positive → acute HIV 1 infection likely].
    • Ak against HIV type 1/2

    Two-step diagnostics according to the recommendations of the DVV: Serological screening with subsequent confirmatory diagnostics by antibody-based test systems such as Western blot (Westernblot; also immunoblot, English) and / or by HIV NAT (nucleic acid amplification test = polymerase chain reaction (PCR examination): direct detection of viral nucleic acid in the blood).

  • Previous HIV screening test (ELISA) [diagnostic gap: 12 weeks]:
    • Ak against HIV type 1/2
    • A positive result should be confirmed by sending a 2nd sample.

    If positive: a positive HIV test result may only be reported after confirmation of the ELISA result in the HIV Western blot (immunoblot).

  • HIV RNA (HIV RNA, quantitative; synonyms, HIV-1 PCR quantitative, HIV-1 viral load) – measurement of the genetic information of the HI virus; falls out in the case of infection one to two weeks earlier than the current HIV search testIndications:
    • Patient with confirmed or highly probable exposure 1-3 weeks ago and/or.
    • Symptomatology of an acute retroviral syndrome.
    • During the course of the disease, to be able to follow the evolution.

    If positive: testing of a second sample and confirmation by serological follow-up Attention! A negative PCR result at this time cannot exclude HIV infection, as the risk of a false-negative result is greater compared to serological detection methods

  • HIV-DNS (HIV-DNA)*
  • HIV isolation – not performed in routine.
  • CD4-positive lymphocytes – determination of the so-called helper cells; gives an important indication of the immune status of the affected person; is measured repeatedly during the course of the disease to be able to follow the development

* The advantages of direct virus detection by HIV DNA are small. An HIV infection can be detected with this test theoretically about 5-8 days earlier. However, the test can then become negative in later stages, although HIV infection has occurred and the antibodies remain detectable. The direct or indirect detection of HIV is notifiable according to the Infection Protection Act (IfSG). Note: The patient must consent before the HIV test is performed (documented consent). HIV detection procedures in chronological order.

Phase Procedure
I HIV RNA by PCR (positive 1-2 weeks earlier than antibody screening testNote: If acute HIV infection is suspected before seroconversion, detection of type-specific HIV RNA is possible no earlier than 10 days after the infection event.
II In addition to phase I: p24 antigen by ELISA.
III Antibody screening tests (ELISA)Note: p24 detection is complicated by the appearance of antibodies.
IV Western blot indifferent
V Western blot positive
VI Western blot fully formed, p31 is now also detectable

Serological parameters in HIV infection

Overview of possible constellations of laboratory diagnostic results and their evaluation:

Virus detection HIV-RNA / HIV antigen HIV antibody detection (immunoblot) Infection status
positive negative acute infection
positive questionable acute infection
positive positive acute or chronic infection
negative positive Chronic infection (usually on antiretroviral therapy)

2nd order laboratory parameters – depending on the results of the medical history, physical examination, etc. – for differential diagnostic clarification

  • HIV resistance tests – examines the sensitivity of the viruses to the various drugs.
  • Opportunistic infections
    • Serology: amoebic dysentery, aspergillosis, coccidioidosis, cytomegaly, EBV, hepatitis A, B, and C, herpes simplex, histoplasmosis, legionella, syphilis (lues), toxoplasmosis (obligatory testing in pregnant women), varicella-zoster
    • Bacteriology (cultural): sputum and urine for common pathogens and mycobacteria; stool for Salmonella, Shigella, Campylobacter, Yersinia.
    • Direct detections: Aspergillus, Pneumocystis carinii, Legionella in bronchoalveolar lavage (BAL; method of sample collection used in bronchoscopy (lung endoscopy)) (sputum if necessary); amoebae, Cryptococcus neoformans in serum and cerebrospinal fluid, Candida, Cryptosporidia, isopores, lamblia and other parasites (e.g. microsporidia) in stool.

Indicator diseases

Indicator diseases, i.e., diseases associated with an increased likelihood of HIV infection (HIV prevalence > 0.1%):

Laboratory diagnostics in known HIV infection

Laboratory parameters 1st order – obligatory laboratory tests [initial examination].

  • Small blood count
  • Differential blood count
  • Inflammatory parameters – CRP (C-reactive protein) or ESR (erythrocyte sedimentation rate).
  • Neopterin (signal messenger produced by macrophages/eating cells; early detection of opportunistic infections).
  • Electrolytes – calcium, chloride, potassium, magnesium, sodium, phosphate.
  • Total protein
  • Electrophoresis
  • IgA, Ig G, IgM, IgE
  • Liver parameters – alanine aminotransferase (ALT, GPT), aspartate aminotransferase (AST, GOT), glutamate dehydrogenase (GLDH) and gamma-glutamyl transferase (gamma-GT, GGT), alkaline phosphatase, bilirubin.
  • Renal parameters – urea, creatinine, cystatin C or creatinine clearance, if necessary.
  • Beta-2 microglobulin
  • Lymphocyte differentiation:
    • CD4 absolute count
    • CD4/CD8 ratio
  • HIV RNA PCR (quantitative; synonyms, HIV-1 PCR quantitative, HIV-1 viral load).
  • Hepatitis serology (HBV diagnostics, HCV diagnostics).
  • Lues serology (syphilis; venereal disease).
  • Cryptococcosis antigen in serum (fungal infection).
  • Cytomegalovirus serology (CMV serology).
  • If necessary, clarification of other opportunistic infections (see above).

Follow-up examinations (minor immunodeficiency: semiannually; moderate immunodeficiency: every 2-4 months; severe immunodeficiency: monthly):

  • Small blood count
  • Differential blood count
  • Inflammatory parameters – CRP (C-reactive protein) or ESR (erythrocyte sedimentation rate).
  • Urinalysis – once a year urinstix examination (if known kidney disease or therapy with tenofovirdisoproxil (TDF) with boosted PI (protease inhibitor) every three to six months).
  • Neopterin (signaling messenger produced by macrophages/eating cells; early detection of opportunistic infections).
  • Total protein
  • Electrophoresis
  • IgA, Ig G, IgM,
  • Liver parameters – alanine aminotransferase (ALT, GPT), aspartate aminotransferase (AST, GOT), glutamate dehydrogenase (GLDH) and gamma-glutamyl transferase (gamma-GT, GGT), alkaline phosphatase, bilirubin due to therapy with antivirals with hepatotoxic effect.
  • Renal parameters – urea, creatinine, cystatin C or creatinine clearance if necessary.
  • Beta-2-microglobulin (β2-microglobulin).
  • Lymphocyte differentiation:
    • CD4 absolute count
    • CD4/CD8 ratio
  • If (CD4-positive) T helper cells < 100/µl in addition:
  • HIV RNA PCR (quantitative; synonyms, HIV-1 PCR quantitative, HIV-1 viral load).
  • If necessary, clarification of opportunistic infections (see above).