What is the National AIDS Control Organisation (NACO) HIV‑testing strategy?

NACO HIV Testing Strategy

The National AIDS Control Organisation (NACO) of India employs a serial rapid testing algorithm using three different HIV rapid test kits in sequence to diagnose HIV infection, with specific protocols for different testing scenarios and populations.

Core NACO Testing Algorithm

The NACO strategy utilizes a three-test serial algorithm for HIV diagnosis in India:

• Test 1 (T1): Initial screening with a highly sensitive rapid test (typically Alere Determine HIV-1/2) 1
• Test 2 (T2): If T1 is reactive, perform a second rapid test with different antigen/antibody composition (typically Unigold HIV-1/2) 1
• Test 3 (T3): If T1 and T2 are discordant, perform a third rapid test as tie-breaker (typically STAT-PAK) 1

Interpretation Rules

• HIV-positive diagnosis: Individual is reactive on T1 AND either T2 or T3 (tie-breaker) 1
• HIV-negative: Non-reactive on T1, or reactive on T1 but non-reactive on both T2 and T3 1
• Indeterminate: Requires repeat testing after 14 days or supplemental testing 1

Testing Protocol by Clinical Setting

Antenatal Care (PPTCT Services)

All pregnant women must undergo HIV testing as part of routine antenatal care:

• Pretest counseling is mandatory before testing 1
• Testing follows the standard three-test NACO algorithm 1
• Posttest counseling must be provided regardless of result 1
• HIV-positive women receive immediate antiretroviral prophylaxis 1
• Newborns of HIV-positive mothers receive nevirapine syrup prophylaxis 1
• Follow-up includes DNA PCR testing of dry blood samples at 6 weeks and 18 months for infant diagnosis 1

High-Risk Populations and Targeted Testing

NACO recommends more frequent testing (every 3-6 months) for:

• Men who have sex with men with multiple or anonymous partners 2
• Persons who inject drugs 2
• Sex workers 2
• Individuals with incident sexually transmitted infections 2
• Sexual partners of HIV-infected persons 2

Critical Quality Assurance Considerations

Known Algorithm Limitations

The NACO three-test rapid algorithm has documented performance issues:

• Concordance between T1 and T2 can be as low as 56.6% in field conditions 3
• Positive predictive value of approximately 94.5%, meaning false-positive rate of ~5.5% 3
• Performance is significantly better under controlled laboratory conditions versus field settings 4
• Discordant results between first and second tests are common and require careful interpretation 3, 4

Essential Quality Control Measures

To minimize false results, NACO protocols require:

• Use of only NACO-approved rapid test kits with proper storage conditions 4
• Regular training and competency assessment of testing personnel 4
• Integrated supportive supervision at testing sites 4
• Comparison against gold standard (Western blot or supplemental assays) for quality assurance 4
• Documentation of all discordant results for algorithm performance monitoring 4

Special Populations

Infants Born to HIV-Positive Mothers

Standard antibody tests cannot be used for definitive diagnosis in infants <18 months:

• Maternal antibodies cross the placenta and persist up to 18 months 5, 6
• Definitive diagnosis requires two positive HIV DNA PCR tests on separate specimens 5
• Testing schedule: First DNA PCR at 6 weeks of age, second at 18 months 1
• Antibody testing only becomes reliable after 18 months of age 5

Acute HIV Infection

When acute HIV infection is suspected (recent high-risk exposure with compatible symptoms):

• Standard rapid antibody tests may be negative during the window period 6
• HIV RNA testing (PCR or bDNA) must be performed urgently in conjunction with antibody testing 6
• Positive RNA with negative/indeterminate antibody confirms acute infection 6
• Immediate referral to HIV specialist for consideration of antiretroviral therapy 6

Counseling Requirements

Pretest Counseling Components

NACO mandates pretest counseling that includes:

• Information on HIV transmission routes 2
• Explanation of the testing process and what results mean 2
• Importance of obtaining test results 2
• Voluntary nature of testing with right to decline 2
• Confidentiality assurances 2

Posttest Counseling

All tested individuals must receive posttest counseling:

• HIV-negative individuals: Risk reduction strategies and prevention counseling 2
• HIV-positive individuals: Immediate linkage to comprehensive medical evaluation, behavioral and psychosocial services 5, 7
• Counseling should not be a barrier to testing but must address transmission prevention 2

Common Pitfalls to Avoid

Never diagnose HIV based on a single rapid test alone - all reactive screening tests must be confirmed through the complete algorithm before diagnosis 5

Do not rely on antibody tests during the window period - recent infection within 6 months can yield false-negative results 5, 6

Avoid testing without proper counseling infrastructure - both pretest and posttest counseling are mandatory under NACO guidelines and essential for linkage to care 1

Do not ignore discordant results - when T1 and T2 disagree, the tie-breaker T3 is mandatory, not optional 3, 4

Never skip quality control procedures - the algorithm's accuracy depends heavily on proper kit storage, trained personnel, and adherence to testing protocols 4