Hiv testing interpretation

Hello,

I would like to ask for an infectious disease specialist’s opinion regarding my HIV testing after a single risky exposure on **May 1, 2018**. My main concern is one result from 2022, where the quantitative PCR was reported as **<48 IU/mL**.

All of my HIV tests were performed at either **ZTM (Blood Transfusion Centre of Slovenia)** or **IMI (Institute of Microbiology and Immunology in Ljubljana)**. The only exception was in 2022, when I had a Western blot, a qualitative PCR, and a quantitative PCR performed in Belgrade at **BeoLab**.

Chronologically, I had the following HIV tests:

* **May 14–15, 2018** – HIV-1 RNA NAT: **non-reactive/negative**.
* **June 12, 2018** – combined HIV Ag/Ab test (anti-HIV-1/2/O + p24 Ag), performed at **ZTM**: **non-reactive**.
* **June 26, 2018** – anti-HIV-1/2/O + p24 Ag, **ZTM**: **non-reactive**.
* **July 23, 2018** – anti-HIV-1/2/O + p24 Ag, **ZTM**: **non-reactive**.
* **February 4–5, 2019** – anti-HIV-1/2/O + p24 Ag, **IMI**: **non-reactive**.
* **February 6, 2019** – anti-HIV-1/2/O + p24 Ag, **ZTM**: **non-reactive**.
* **February 11, 2019** – HIV-1 RNA PCR, quantitative, **IMI**: **NEGATIVE**. On the same occasion, another anti-HIV-1/2/O + p24 Ag test was performed and was also **negative**.
* **February 11, 2019** – HIV-2 DNA PCR, **IMI**: **NEGATIVE**.
* **April/May 2019** – I donated blood at **ZTM**. As far as I know, donated blood is screened for HIV using both Ag/Ab testing and NAT. I was never informed of any reactive result, although I do not have the actual laboratory report from that donation.
* **February 5–7, 2020** – anti-HIV-1/2/O + p24 Ag, **ZTM**: **non-reactive**.
* **January 17–19, 2022** – HIV Ag/Ab + p24 Ag screening test, performed at **IMI**: **non-reactive**.
* **February 28, 2022, BeoLab Belgrade – HIV-1+2 Western blot:** **NEGATIVE**, with all listed protein bands negative.
* **February 28, 2022, BeoLab – HIV-1+2 qualitative PCR:** **NEGATIVE**, with a stated lower limit of detection of **20 IU/mL**.
* **February 28, 2022, BeoLab – HIV-1+2 quantitative PCR:** result **<48 IU/mL**, with a stated quantification range of **48–10,000,000 IU/mL**.

My main question concerns the last result:

**What exactly does “<48 IU/mL” mean?**

Does a quantitative PCR result of `<48` simply mean that the viral load could not be quantified above the assay’s lower limit of 48 IU/mL, or can it also mean that HIV RNA was actually detected but was below the limit of quantification?

If HIV had truly been detected below the quantification limit, would the laboratory not usually report something like **“detected below LOQ”** or **“positive below the limit of quantification”**?

How should this `<48` result be interpreted considering that, on the same day, the **qualitative HIV-1+2 PCR was NEGATIVE (LOD 20 IU/mL)** and the **Western blot was NEGATIVE**, while before that I had numerous negative combined Ag/Ab tests at ZTM/IMI performed months and years after the exposure?

Based on this entire sequence of tests, can HIV from the exposure on **May 1, 2018** be considered medically ruled out, and does the `<48 IU/mL` result have any clinical significance in this context?

There were **no further risky exposures after that event**.

Thank you very much for your professional interpretation.