HIV (I & II)-Human immunodeficiency virus Screening

Clinical definition of the HIV screening test
HIV (human immunodeficiency virus) is a virus that kills or damages the body's immune system which can lead to serious infections that don't often affect healthy people. HIV enters the body through unprotected sex with an infected person via semen or vaginal fluid, contact with the blood of an infected person, sharing drug needles or via pregnant women to their babies during pregnancy. Infection with HIV causes AIDS. AIDS stands for acquired immunodeficiency syndrome and is an advanced form of an HIV infection. It can be prevented by practicing safe sex or by having AIDS medicines too. The commonly performed HIV tests are:

  • HIV DUO (Elisa) - To screen for HIV infection
  • Western Blot- To confirm for HIV infection
  • HIV COMBO-To check for Viral load & CD4 cell count

Why is the HIV screening test done?
HIV ELISA/Western blot is a set of blood tests used to diagnose and screen infection with the human immunodeficiency virus (HIV) in serum, saliva or urine. Such tests may detect HIV antibodies, antigens or RNA.
Any blood test related to HIV conducted during the window period may give false negative results.  A window period is the time it takes for the body to produce HIV antibodies after infection with the virus. In most people, this period is between 2weeks and 12 weeks.

What are the common signs/symptoms when the HIV screening test is done?

HIV infection mostly goes unnoticed & without symptoms in the early stages. People who get the virus may develop a brief cold or flu-like illness 2 to 6 weeks after becoming infected.  The immune system of the individual may get severely affected beginning with mild infections or further develop into chronic symptoms such as:

  • Swollen lymph nodes
  • Weight loss 
  • Fever 
  • Cough 
  • Shortness of breath 

During the late HIV stage, more serious symptoms may start to appear such as:

  • Swelling of lymph nodes for over 3 months 
  • Chronic diarrhea 
  • Lasting headaches 
  • Persistent, unexplained fatigue 
  • Soaking night sweats 
  • High fever (greater than 100°F) & chills for several weeks 

Who should do the HIV screening test (Target population)?
Persons who are at a high risk of developing the disease due to unsafe sex, sharing of needles or by pregnant women suspected of transferring the infection to her baby.

What should I do before the HIV test?

Specimen type

Specimen collection procedure

Preparatory instructions before the test *

Serum (Blood Sample)

Venipuncture - Collection of blood from a vein, usually from the arm.

No Fasting Required.

No other special preparations required.

*Subjects suffering from any illness or on oral or injectable medications are advised to consult their physician prior to requesting any tests or procedures.

How do I interpret my HIV screening test results?

HIV-DUO (serum)

Reference Range*


Above 1.0 Index


0.0 to 1.0 Index

Non Reactive

Inference: A positive ELISA screening test does not necessarily indicate an HIV infection. Certain other conditions such as Lyme disease, syphilis and lupus may lead to a false positive result. A positive ELISA test is always followed by a Western blot test. A positive Western blot confirms an HIV infection. A negative Western blot test would indicate that the ELISA test was a false positive test.
‘*A Reference range is a set of values which helps the healthcare professional to interpret a medical test. It may vary with age, gender, and other factors. Reference ranges may also vary between labs, in value & units depending on instruments used and method of establishment of reference ranges’

Diseases/conditions related to the HIV screening test

  • Tuberculosis 
  • Hepatitis
  • Candidiasis
  • Cryptococcal meningitis, 
  • Pneumocystis carinii pneumonia (PCP)
  • Histoplasmosis,
  • Cryptosporidiosis
  • Toxoplasmosis

Other tests related to the HIV screening test

  • Western Blot
  • p24 antigen test
  • CD8 cells
  • HIV viral load
  • HIV genotypic resistance testing

Synonyms : Cobas taqman
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