Importance of Tube Used For HIV Test
Nov 18, 1996
I recently tested negative for HIV on an HIV antibody test taken four months after possible exposure to the virus. I realize that six months is the window period considered to be nearly definitive for an HIV antibody test result, so I understand that the results that I've received from this test cannot be considered conclusive at this juncture. However, what is compounding my anxiety even at this stage, despite the negative result, is a note at the bottom of the test report (the test was performed at Labcorp in Raritan, NJ, formerly Roche Biomedical Labs) stating: "Submission of serum separator tube recommended for this test." Such a notation naturally leads me to believe that the blood specimen submitted for analysis was in a type of tube other than an SST, the recommended kind, and this leads me to wonder whether that might in any way compromise the validity of the results that I received. Additionally, the date of the report is Oct. 23--9 days after the blood for the test was drawn, causing me to question whether the blood was still fresh enough to yield an accurate result if, in fact, it wasn't assayed until, say, 8 or even 9 days after it was drawn. Given your considerable experience in the field of HIV testing, you're someone that I thought would truly possess the expertise to shed meaningful light on an issue such as this one, and so I would deeply appreciate your telling me whether the circumstances that I have described above could in any way render my test results potentially invalid. One could presume that personnel at a facility with the reputation of Labcorp/Roche would not attach their name, or the company's, to a finding unless it was deemed to be accurate and unless all of the testing conditions and procedures were considered proper, BUT I would nevertheless be grateful for your input on the matter. Thanks very much for all of your help.
Response from Mr. Sowadsky
Hi.Thank you for your question.
When labs are performing HIV antibody tests, the specimens could be submitted to the lab either as whole blood, or in a serum separator tube. Using a serum separator tube is not manditory when drawing blood for this test.
The period of time from when the blood was drawn to when the blood can still be tested, varies on the specific circumstances. If the specimen is not refrigerated, the specimen is good for one week. If it is refrigerated or frozen, the specimen can be good for weeks or even months. The policy of one of our local labs is that they will accept a refrigerated/frozen sample up to 1 month after it's collection. Normally labs receive the specimens with a day or so after the collection date. The turnaround time from collection to lab results averages about a week. If a specimen is too old, or if there are other problems with the specimen (such as if there's not enough blood in the sample to run the test, or it was drawn in the wrong type of tube), the lab will often reject the sample, and not do the test. So if the lab ran your test, it would be unlikely that there was a problem with the specimen itself.
If you have any further questions, please feel free to call the Centers for Disease Control at 1.800.232.4636 (Nationwide). Rick Sowadsky MSPH CDS
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