Test gets almost 1 in 5 syphilis cases wrong

[Viva_La_Revolution]

Source: AP

Hundreds of people may have been told they tested positive for syphilis when they didn't actually have the disease, health officials say.

A study of five U.S. labs shows about 18 percent of the positive results from a test method used since the 1980s were actually negative, the Centers for Disease Control and Prevention said Thursday.

The CDC recommends additional testing when this particular test gives a positive result. But even if most doctors retest, the new research suggests that some people have unnecessarily worried they were infected with an infamous sexually transmitted disease.

It also may mean some patients have been given unnecessary treatment — probably penicillin, which can have side effects.

Read more: http://hosted2.ap.org/apdefault/d30f3f32e9d849979111e891380b64db/Article_2011-02-10-Syphilis%20Test/id-8f07bf0eb414474a82df17ad1575a24d

[midnight]

1. Labs that are not checking their error rates are just as dangerous as they things being tested for.

Where are our quality control agencies?

[du_grad]

4. This is not necessarily lab error

http://www.cdc.gov/mmwr/preview/mmwrhtml/mm6005a1.htm?s_cid=mm6005a1_w

I have been a medical technologist since 1974. When I learned to perform basic syphilis serologies we did the RPR test. If this was positive, a test called FTA-ABS was done to confirm the positive, as RPR's do have some cross-reactivity with other disease states. This fact has been known for a long time. The other test that was performed for syphilis testing is the VDRL. This is a manual test that requires a bit more finesse in performance than an RPR. I can remember performing 50+ RPR's per day, as back then, we did them on all new admits. We kept track of the positives. Follow-up testing with the FTA-ABS test was not done that often.

This testing issue is much more complex than what is stated in the lead article. Labs are looking for methods that are automated and accurate that can be performed on hundreds of specimens per day (in the case of large reference laboratories). This article is about methodology, not lab error.

I am familiar with some of the terminology in the article cited above, but I will admit that I would have to sit down and really study it before I understand it. If you have no medical or lab background, I guarantee you will have problems understanding the jargon and the issues.

Please do NOT assume that it is always the lab's fault. It is a very regulated industry. We perform controls on testing that requires them and inspectors always look at QC logs first. Labs are inspected by JCAHO, CAP, State health departments and other entities, depending on what type of lab it is and what testing is performed there.

[laconicsax]

2. On the positive side, false positive is better than a false negative...

[MannyGoldstein]

3. It's typical of a screening test

But should be followed by a more-definitive test.

[truthisfreedom]

6. Hear, hear!

[truthisfreedom]

5. Patients should be told to re-test immediately after a positive to see if it's false.

That's the solution, if the test MUST be used.

[laconicsax]

7. Depending on who's doing the original test, positives are always retested to confirm.

The Red Cross will test blood for syphilis, positives are retested and the blood is ditched regardless.