Guidance

Results table and reporting comments for HIV

Updated 25 May 2022

Applies to England

The table below shows different testing results. For each set of results, clinical comments for reports and recommendations for the laboratory team are outlined below the table.

Result	HIV Ag/Ab screen	2nd HIV Ag/Ab assay	Typing assay HIV-1	Typing assay HIV-2	HIV-1 RNA (if performed as reflex test or on further sample)
1	Not detected	Not required	Not required	Not required	Not applicable
2	Detected	Detected	Detected	Not detected	Not applicable
3	Detected	Detected	Not detected	Detected	Not applicable
4	Detected	Detected	Detected	Detected	Not applicable
5	Detected	Not detected	Not detected	Not detected	Not applicable
6	Detected (repeat sample as follow-up to results in 5)	Not detected	Not detected	Not detected	Not applicable
7	Detected (following flowchart for sequential confirmatory testing)	Not detected	Not tested	Not tested	Not applicable
8	Detected (repeat sample as follow-up to results in 7)	Not detected	Not tested	Not tested	Not detected (separate follow-up EDTA sample)
9	Detected	Detected	Not detected	Not detected	Not applicable
10	Detected (repeat sample as follow-up to results in 9)	Detected	Not detected	Not detected	Not detected (separate follow-up EDTA sample)
11	Detected	HIV antibody detected but p24 antigen not detected	Not detected	Not detected	Not applicable
12	Detected	HIV antibody detected but p24 antigen not detected	Not detected	Not detected	Not detected (reflex test on original screening sample)
13	Detected (repeat sample as follow-up to results in 11)	HIV antibody detected but p24 antigen not detected	Not detected	Not detected	Not applicable
14	Detected	Not detected	HIV-1 and/or HIV-2 antibodies detected	HIV-1 and/or HIV-2 antibodies detected	Not applicable

Result 1

For this result, the clinical comments to report are:

• HIV-1 and HIV-2 antibody and p24 antigen not detected
• no evidence of HIV infection

When screening tests for all 3 infections are negative/not detected add the following comments:

• negative at time the screening sample was taken
• please offer testing at any time in pregnancy if the woman has a new exposure risk or develops relevant symptoms

Result 2

For this result, the clinical comments to report are:

• HIV-1 antibodies detected
• refer to multi-disciplinary team for full clinical evaluation

Result 3

For this result, the clinical comments to report are:

• HIV-2 antibodies detected
• refer to multi-disciplinary team for full clinical evaluation

If HIV-2 antibody is detected as a new diagnosis, referral to a reference laboratory that undertakes HIV-2 specific serology and HIV-2 RNA testing for confirmation is advised.

Result 4

Although these results suggest co-infection, in practice this is very rare and it’s more likely the assay was unable to differentiate antibodies as HIV-1 or HIV-2. It is advisable to send a sample to the reference laboratory before reporting unless the woman is a late booker.

Result 5

We recommend repeating the screening assay to ensure the result is reproducible. If the result is not reproducible then report as for result 1. If the result is reproducible then the clinical comments to report are:

• HIV inconclusive as positive result in screening assay only and not confirmed in 2 further assays
• probable false positive in the screening assay: to confirm please repeat 2 weeks from the date of this sample

We recommend reporting comments only, not individual test results.

Result 6

For this result, the clinical comments to report are:

• no evidence of HIV infection and no action required
• the sample gives the same reactivity as the previous one: the absence of serological change and the continued negative results in the confirmatory assays indicate that the result in the screening assay is non-specific

Use these comments when the first sample was inconclusive and the repeat sample 2 weeks later gives the same results.

We recommend reporting comments only, not individual test results.

Result 7

We recommend repeating the screening assay to ensure the result is reproducible. If the result is not reproducible then report as for result 1. If the result is reproducible the clinical comments to report are:

• HIV inconclusive as positive result in screening assay only and not confirmed in one further assay
• probable false positive in the screening assay: to confirm please send a repeat serum and 3 EDTA for HIV viral load a minimum of 2 weeks from the date of this sample

The above comments can be modified if the sample types and quantity required for a local laboratory differ.

We recommend reporting comments only, not individual test results.

Result 8

For this result, the clinical comments to report are:

• no evidence of HIV infection and no action required
• the sample gives the same reactivity as the previous one and the confirmatory Ag/Ab assay remains negative as is the HIV viral load; this indicates that the result in the screening assay is non-specific

Use these comments when:

• the first sample is positive in the screening assay but negative in the second Ag/Ab assay and
• the repeat sample 2 weeks later gives the same results and
• the HIV viral load is not detected

We recommend reporting comments only, not individual test results.

Result 9

For this result, the clinical comments to report are:

• serology for HIV is inconclusive but acute infection with HIV cannot be excluded
• please send 3 EDTA for HIV viral load as soon as possible and a repeat serum sample 2 weeks from the date of this sample

The above comments can be modified if the sample types and quantity required for a local laboratory differ.

The other clinical comments to report are:

• please assess risk of acute infection and refer to multi-disciplinary team for full clinical evaluation
• please ask patient about recent exposure risks, history of antiretroviral drug use (including pre and post exposure prophylaxis), participation in HIV vaccine trial or any condition affecting the immune system, as these can affect test results, and inform the laboratory if any of these apply

Result 10

For this result, the clinical comments to report are:

• no evidence of HIV infection
• no action required
• the sample gives the same reactivity as the previous one and the typing assay remains negative as is the HIV viral load; this indicates that the result in the screening assay and confirmatory Ag/Ab assay is non-specific

Use these comments when:

• the first sample was low positive in both Ag/Ab assays, negative in the typing assay and
• the repeat sample 2 weeks later gives the same results and
• the HIV viral load is not detected and
• the answers to the patient questions in scenario 7 are all ‘no’ (if any of the answers are ‘yes’ suggest discussion with reference laboratory)

Report comments only, not individual test results.

Result 11

For this result, the clinical comments to report are:

• both Ag/Ab assays are positive and the typing assay is negative; while this might represent early infection it is more likely to be a false positive as the p24 component of assay (insert name of assay used) is negative
• please send a repeat sample 2 weeks from the date of this sample
• please ask patient about recent exposure risks, history of antiretroviral drug use (including pre and post exposure prophylaxis), participation in HIV vaccine trial or any condition affecting the immune system, as these can affect test results, and inform the laboratory if any of these apply

Only use these comment when:

• both Ag/Ab assays are low positive and
• the typing assay is negative and at least one of the Ag/Ab assays gives a breakdown of the components of the result, indicating that the p24 antigen is negative, and
• the clinical microbiologist or virologist is confident in discussing the result directly with the screening team

We recommend reporting comments only, not individual test results.

Result 12

For this result, the clinical comments to report are:

• no evidence of HIV infection
• although both Ag/Ab assays are positive and the typing assay is negative, suggestive of early infection, this can be excluded because both the p24 component of assay (insert name of assay used) and the HIV viral load are negative
• the Ag/Ab assays are therefore false positive results
• please ask patient about any history of antiretroviral drug use (including pre and post exposure prophylaxis) as this can affect test results and inform the laboratory if any of this applies as results will require review

Only use this report when (in addition to the comments above) the laboratory is able to reflex test from the screening sample to an HIV viral load assay and this is not detected. This gives a definitive negative result and a repeat sample is not required.

We recommend reporting comments only, not individual test results.

Result 13

For this result, the clinical comments to report are:

• no evidence of HIV infection and no action required
• the sample gives the same reactivity as the previous one and the typing assay and p24 component of assay (insert name of assay used) remain negative; this indicates that the result in the screening assay and 2nd Ag/Ab assay is non-specific

Use these comments when the first sample was low positive in both Ag/Ab assays, negative in the typing assay and the repeat sample 2 weeks later gives the same or lower results.

We recommend reporting comments only, not individual test results.

Result 14

Highly unusual pattern of results. Likely to be a false positive. It is advisable to send a sample to the reference laboratory before reporting.