[HIV] How do I interpret S/CO values?

[HIV] How do I interpret S/CO values?

I've had 3 HIV tests performed in 2 hospitals.
How do I interpret the S/CO values?

* Test 1 (18 July 2007):
Hospital A
Anti HIV 1/2 gO - MEIA
Patient's Value: 0.37
Cut-Off Value: 1.00
Result: Non-reactive

* Test 2 (19 November 2007):
Hospital B
HIV 1/2: 0.37 S/CO (NEGATIVE)

* Test 3 (09 January 2008):
Hospital B
HIV 1/2 GO: NEGATIVE
0.44 S/CO

All tests returned NEGATIVE. Test 1 and Test 2 were performed in different hospitals, but have the same S/CO values, 0.37. Meanwhile, Test 2 and Test 3 were performed in the same hospitals, but had different S/CO values (presented in different formats), the second one higher than the first.

1. Should I be alarmed about this increase in value?
2. Is there any possibility an HIV test in the future will be POSITIVE? Last sexual contact was on 05 May 2007.

No, you should not be alarmed, because the cut off values are a measure of the controls used for your test, and have nothing to do with your sample. Every time a batch of HIV tests are done, extra specimens are added that are calibrated negatives and positives, their specific values are known. Minor variations in the test can result in very small changes in end results of the test, patient values of 0.37 vs 0.44 is an example of those variations. These known controls are used to calculate the cut off for the day, the values that determine if a specimen is positive or negative. Anything close to this cut off is considered borderline, and the patient sample is tested again. There is no such thing as a zero score, that's not how the test works. But your specimen's value was 37% of the cutoff, which is considered a total negative. It does not mean that you had a little HIV reaction, it is just a variation in the testing procedure.

The fact that you got 0.37 for a value the first two times is coincidence, if you tested the same blood draw multiple times, you would get multiple results.

Your results tell you that you are negative. According to a friend who is trained HIV counselor. HIV can be detected in as early as 4 months after last contact. You have you last contact 2007 may, most probably you are negative.

Be careful next time friend.

You should not be alarmed at all. All the tests show a NEGATIVE result. (non-reactive).

The window period (the time inbetween infection and before testing positive) for HIV is as follows:

75% of people will test positive by 17 days after infection
95% of people will test positive by 2 months after infection
OVER 99% of people will test positive by 3 months.

The fraction of a percent who won't test positive by 3 months include people who, for the most part, have already compromised immune systems (radiation treatments, transplant recipients) or a few other extremely rare conditions.

Virtually everyone will test positive by 6 months