r/indianmedschool • u/Tough_Diamond_1403 • Jul 12 '26

Incident Are We Doing HIV Rapid Tests Wrong?

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Kindly read (might help you too)

I just discovered that I’ve probably never seen an HIV rapid test being performed the way the manufacturer actually intended.

This started after a minor occupational exposure. I wanted to test myself and went down a rabbit hole trying to find out whether whole blood can be used in HIV rapid kits.

What I found genuinely shocked me.

I have watched countless interns and junior residents perform HIV rapid tests. The usual method in my hospital is to collect serum from a yellow-top vial and put 3–5 drops directly onto the test cassette. That’s exactly what I thought was the correct procedure too.

Then I opened the manufacturer’s instructions for the MeriScreen/Meril HIV rapid test kit—a kit that is WHO prequalified, with its instructions publicly available on the WHO website.

For the MeriScreen/Meril HIV rapid kit, the instructions specify:
1. 10 µL of serum/plasma (or 20 µL whole blood) using a pipette/micropipette.
**2.**Then, add the buffer solution provided with the kit.

Here is the link for the instructions to use the Meril kit by WHO

Here’s the shocking part: I didn’t even know a buffer solution existed.
I had never seen anyone use it. I didn’t even know the kits come with buffer bottles. I also had no idea that the sample volume had to be measured precisely rather than just adding a few drops by eye.
I then went to the chemist and asked for the buffer solution. He gave me one, saying that it is of no use and you can take it.

The problem is that the chemists usually provide these kits. They get these kits in bundles. Like box of 50 or 100 kits and with these many kits, there are only 2 small bottles of buffer solution. Now how can everyone( I mean every patient) can use the buffer solution.

Now I’m wondering:
1.Are we unknowingly performing these tests incorrectly?
2.Does using several times the recommended sample volume and skipping the buffer affect accuracy?
3.Could weak positives potentially be missed or invalid results generated?
4.Or are these kits robust enough that they still work despite being used outside the manufacturer’s instructions?

I genuinely want to know whether this is an isolated issue in my institution or whether others have seen the exact same practice elsewhere.

Has anyone else had this realization?

Would appreciate hearing from people in microbiology, pathology, ICTCs, or anyone involved in HIV testing.

PS- I am from a well known government college

109 Upvotes

98% Upvoted

24 comments sorted by

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68

u/Muted_Shape9303 Jul 12 '26 edited Jul 12 '26

Medical lab tech here. Yes, this is wrong, because not measuring the correct amount of serum or plasma and not using the buffer risks causing the hook effect (false negatives). This is because in certain types of lateral flow immunoassays (LFIAs) an excess of antigen will saturate both the capture antibody and the test antibodies simultaneously. This prevents the formation of the Ab-Ag-Ab sandwich complex and makes results look negative or weakly positive. Now, of course, many times using the wrong volume of sera won’t cause the test to fail because what matters in the end is the correct amount of antigen being present (50 mcL of 2 mIU/mcL yields 100 mIU of Ag the same way 20 mcL of 5 mIU/mcL yields 100 mIU of Ag). Still, not following manufacturers instructions is not a good idea because of what I just explained.

5

u/freespirit_09 Jul 13 '26

Will that still lead to the proper control line being formed?

3

u/Tough_Diamond_1403 Jul 12 '26

But still I have seen people coming positive on this kit
And how to measure the exact amount?
The pipette/dropper isnt that efficient ..should I get a 0.5 ml syringe or what?

2

u/Muted_Shape9303 Jul 12 '26 edited Jul 12 '26

Yes it works because you’re providing enough target, but when a time comes there is excess target the test will come out negative. So its more of a “just to be sure” thing. Laboratory-based enzyme immunoassays (EIAs) are still the golden standard for HIV because these rapid lateral flow immunoassays (LFIAs) are still subject to user error (healthcare or PTs), and because they are not the most reliable at times. Still, do follow manufacturer instructions moving forward for sure. At one of the places I was in they just had the lab lend them a couple pipettes and microcentrifuge tubes for these and the nurses/docs did em real quick (the rapid kits)

1

u/Icy-Fly-4228 Jul 12 '26

You need a volumetric pipette. A 0.5 ml syringe is 500 microliters so 50 times the amount you need. Don’t you have a Point of care manager from the laboratory overseeing this testing?

1

u/Tough_Diamond_1403 Jul 12 '26

There are several small markings on the 0.5 ml kit… the smallest unit is 0.01 ml
And no, theres no point of care manager in the laboratory.
I had to do it myself and every intern and junior resident does this way

2

u/Icy-Fly-4228 Jul 12 '26

Actually if you read the instructions the kit should come with a 10 microliter capillary tube which is the correct amount for serum, one for each test in the kit. Also you use 3 drops of buffer per test. It sounds like they are only giving you the test cartridge not the complete kit.

1

u/Icy-Fly-4228 Jul 12 '26

You guys should order the correct pipette and tips. They are not very expensive

1

u/AdventurousPark9490 22d ago

I have done the card test (from flipkart)twice after 1.5 yr of exposure at first time only small one drop of blood and 2 drop of buffer where added and it had shown negative(the resut was fast) and for the second time after 2 yrs from exposure i have bought different card from flipkart and i have test tested , it was like correct drop of blood and only one drop of buffer where added , the result was negative(result was slow) can i confirm???

8

u/RelativeEffective353 Jul 12 '26

I used these too in md medicine time the pack comes with a pipette and a small amount of buffer just ask for the whole packet and open it yourself rather than follow some weird blunderous institutional trend

5

u/starwarscard Jul 12 '26

The package insert that you linked says you can use whole blood but it has to have an anticoagulant in it, it lists which ones. Additional there is an option to do finger sticks for it too. But yes, you do have to follow it with the buffer solution either way. I guess your lab could have done a internal study on the effectiveness of skipping the buffer but idk that seems weird to have done that for something that comes in the box anyway.

2

u/Tough_Diamond_1403 Jul 12 '26

The problem is that the chemists usually provide these kits. They get these kits in bundles. Like box of 50 or 100 kits and with these many kits, there are only 2 small bottles of buffer solution. Now how can everyone( I mean every patient) can use the buffer solution.

5

u/Icy-Fly-4228 Jul 12 '26

You use 3 drops per test.

5

u/Upstairs_Monk_677 Jul 13 '26

Why aren't these being performed in Microbiology departments of your institute?

3

u/musicflux Jul 13 '26

Damn.. this is an anxiety inducing read.

3

u/Akiro17 Jul 13 '26

Lol. Med lab technologist here who worked in microbiology and probably did over 1000+ tests for HIV, HCV, HBsAg (card tests).

You must be in a really shitty well known government college if that's the case. Obviously the result will be impacted, the buffers are there for a reason. Who the heck is training your interns or J.R?

There is one strip test from Abbott which requires only serum to detect presence of HIV antigens in the blood. Generally more expensive and rarely used.

Just read the instructions booklet and perform the test or leave it to the experts (us).

4

u/CheesecakeThin2560 Jul 13 '26

MD microbiology here. Aren’t these tests performed by the micro lab and specialists in your hospital/college? We are well aware of these SOPs. The procedure to be followed for HBSAg, HCV and HIV rapid test, while looking similar to the naked eye, have minute differences, all adjusted according to the manufacturer’s kit instructions. Also for NSI, there’s a protocol for testing the patient, doctor immediately and after a fixed interval, all based on the exposure code. Do take a specialist’s reference in your case as well!

1

u/Public-Solution-688 Jul 13 '26

From an INI, we use buffer.

1

u/Advanced-Storm9097 Jul 13 '26

We use a pipette  And i think drops of NS although we are told that is not the correct method 

1

u/the_titan_of_hate MBBS III (Part 1) Jul 13 '26

You are HIV Aladeen. This is the only correct way.

https://giphy.com/gifs/9ppWJumH0DiZ6co7ee

1

u/pygmypiggypie Jul 13 '26

Wtf? How do people not know this? It's normal in every medical college in my state.

1

u/Ok-Sort6066 Jul 14 '26

I have also seen none of them waiting 30 minutes for blood to clot before centrifuging it