Anyone ever had a false-positive lab test? I got a health scare this past Monday when my doctor's nurse phoned me the lab results of a full labwork I had done. I had very good liver numbers, I was also negative for HIV, Tuberculosis, Hepatitis A, and Hepatitis B. However, I tested "reactive" on the antibody test for Hepatitis C. For all intents and purposes I am not high-risk for Hepatitis C; I don't do drugs of any kind (least of all the kind you inject) and I don't have any tattoos. I hate needles. The nurse said the doctor wanted a more comprehensive test (PCR RNA to detect the actual virus rather than an immune response to the virus) and had the blood drawn the next day. I would have to wait two days for the results. I went through the whole list of situations where I might have had blood contact with someone. Maybe I cleaned up dirty blood and touched my eyes. Maybe I accidentally pricked myself when I checked my grandma's blood sugar. Maybe my mom (a baby boomer, a group that is at a higher risk for Hep C because of health practices back then) has Hep C and passed it to me and my sister (worst case scenario). The nurse, however, said that even if I had Hepatitis C, we now have on the market a pill treatment that CURES Hepatitis C in 8-12 weeks after taking one pill daily, with minimal side effects with a 95+% efficacy rate, unlike the previous regiment of that required injecting interferon weekly, made you sick as a dog, and only worked on 50% or so of patients. Sure, the pill treatment only would cost $100,000 but you'd be cured. And since I had private insurance I would probably get it for only $5 a month with a coupon card the manufacturer made. Thank you Gilead Sciences/ Harvoni. Well, today I got the lab results back and I have no trace of the actual virus in my body. Whether I fought the virus and eradicated it on my own or never had it, we won't know for sure unless we later do more tests, but for the moment I don't care because it doesn't matter: I don't have Hepatitis C. thank goodness. Anyone ever had a false-positive lab test?
@Alamo-Glad you're healthy! That would put a scare into me. Never had any false-positives, though I have had conditions like dizziness, headaches and once, a rash o my back, and they did 10,000 tests, and din't turn up anything. Rash went away; I found out is was caused by those dryer sheets. Dizziness & headaches are no doubt related to my crazy vision, and eye problems, that have haunted me since college.
No I have had not but this is actually a very interesting topic. False positives and false negatives are not easily grasped concepts even by healthcare professionals as it is a little bit counter-intuitive unless you draw a picture of if. When the prevalence of the actual disease is very low then what actually happens is that significant proportion of positive test results are actually false. For example, only 1/6 of the women whose fetus tests positive for down syndrome actually have a child who is down positive. Let's examine why. I'm just making up numbers here so don't take them too seriously, just get the concept. Suppose a disease X is carried by 0.5% of the total population. Let's suppose that the disease can be detected with 99% accuracy. This means that there is only 1% chance for the test to give you false positive i.e. For simplicity let's assume that the test will not give false negatives. If you take the test and the test is positive what is the probability that you actually have disease X? The answer may surprise some of you. Before checking the spoiler try to assess the magnitude. Spoiler The correct answer is ~33%. Are you surprised? The key into understanding this is the concept of conditional probability and the false positive rate. To put it in layman terms let's imagine there are 1000 people who take the test. 0.5% or 5 of them actually have the disease yet the test false positive rate indicates that on top of the 5 people 1% those of who take the test will test positive even if they don't have the disease. So in addition ~10 people will test positive while they are in fact negative. Classical probability says that the probability of something is the favored case over all relevant cases. Since we are only interested in those who for any reason test positive the equation becomes: 5/(5+~10) = 33% or 0.5%/(1%+0.5%)
Yes, my wife did. Her ex girlfriend kicked her out because of it. After getting retested she was 'allowed' to return home again. Of course she was negative, so these are not that all uncommon.
My parents both tested false positive for hep c when they went to donate blood. their doctors confirmed they didn't have the virus.
Thankfully it's never happened to me. Although my GP thought I had warts when they were actually allergies :lol: YES! Once I washed my sheets with some detergent I hadn't used before and woke up feeling like I have rolled around in poison ivy
False positives, particularly for hepatitis-C, are rare, but not unheard of. If they're doing the initial antibody screen, the reliability rate is about 98-99%, but there are various factors that can increase the likelihood of a false positive. What's a little odd here is that they called you back in for a second blood draw for the PCR. Perhaps they're doing things differently now but back when I was an STI testing counselor, any test that came back positive on the antibody test was automatically retested on the more sensitive test (in those days, before the PCR, it was a Western Blot.) and presumably there was enough blood draw to do both. The thought was, no sense alarming someone when there's a reasonable likelihood it's a false positive, so let's be sure before we report it to the patient. In any case, really glad to hear yours was a false positive.
