HIV test misdiagnosis: How indeterminate Western Blot results can be misdiagnosed.

I Was Misdiagnosed With HIV

I Was Misdiagnosed With HIV

Health and medicine explained.
April 3 2013 4:19 PM

The Week I Had HIV

Misdiagnoses are a rare but intractable problem. Here’s what happened to me.

(Continued from Page 2)

There are a number of reasons why a Western Blot could be indeterminate. Most indeterminate results arise from medical conditions that affect a patient’s blood. Pregnancy, for instance, can cause a Western Blot to find traces of one viral band, called P-24. Autoimmune disorders can cause other viral bands to show up, as can the flu vaccine. Most of the time, these bands disappear in follow-up tests. If they don’t but no further bands show up, the indeterminate result should be considered negative.

But there’s another kind of indeterminate result, one so rare that Dr. Smith had never seen or even heard about it. This result indicates the detection of nonviral bands. These signal an error in the test itself. To run a Western Blot test, lab technicians grow HIV in a cell culture, isolate parts of the virus called antigens, and then expose them to a patient’s blood serum. If the patient is HIV-positive, antibodies in his blood serum react to certain antigens, producing viral bands. But very rarely, the test can malfunction: Lab technicians may insufficiently purify HIV, allowing debris from the cell culture as well as antigens to be exposed to the blood serum. In turn, this debris—rather than the HIV antigens—may react with antibodies. The result: nonviral bands.

These bands do not indicate the presence of HIV. They don’t even hint at it. In 1999, the National Confirmatory Testing Laboratory of the American Red Cross suggested that Western Blots with nonviral bands be considered immediate negatives, since “no individual exhibiting non-viral banding has been associated with either seroconversion detection of different HIV subtypes or other disease agents.” The same year, the Association of Public Health laboratories stated that “non-viral bands should not be required to be reported [because] since 1991 no individual exhibiting non-viral banding has been associated with either early seroconversion, detection of different HIV-I subtypes, or other disease agents.” And in 2000, the Blood Products Advisory Committee of the FDA proposed that nonviral band indeterminate Western Blots be considered completely HIV-negative, and thus safe to use in blood donations.


All of these groups recognized the same fact: Nonviral bands show up as a result of a lab error, not a blood infection. Yet none of their recommendations were ever taken. Many doctors are unaware of the nonviral bands and think them to be a sign of early seroconversion. Because the problem is so rare, it has attracted little research or attention from the press. When a patient receives this anomalous result, he is usually thrust into the formal process of an HIV diagnosis.

There are several ways to tell a patient he has HIV. Some doctors refuse to tell patients over the phone, choosing instead to make an appointment and tell them in person so they can quell the patient’s panic and ask crucial follow-up questions. Others, however, believe that calling a patient and simply asking him to come in to discuss an HIV test is an obvious giveaway of an unwanted result, and that the news should simply be broken immediately, over the phone. This method has the benefit of ensuring that the patient knows his status whether or not he ever follows up. Rapid test immunoassays are quickly solving this conundrum: Clinicians can tell a patient his status in only 20 minutes. Rapid tests are popular in public health clinics but are not yet widely used by most primary care doctors, and so for now, the quandary remains.

Dr. Smith gave me his diagnosis over the phone and scheduled an appointment for the next morning. I spent that evening frozen in terror and confusion: There was simply no way, so far as I could see, that I could have been exposed to HIV. When I told my boyfriend, he was equally baffled: We each dug up the paperwork from our last two HIV tests, both of which were unambiguously negative. Nothing had occurred between those tests and this new one that could have exposed either of us to HIV. But this knowledge did little to allay the panic. We did not sleep that night.

The next morning at my appointment, Dr. Smith reiterated his strong suspicion that I was early into HIV infection and drew blood for a confirmatory RNA test. But he also suggested a rapid test immunoassay, which, by that point, should have turned positive. I sat for 20 minutes waiting for a second line to appear: Rapid tests contain colloidal gold, which reacts to HIV antibodies by producing a red line on a small screen.

As I waited for the test result, I began to think about what my life with HIV would look like. The virus, of course, is no longer a death sentence; those who have it can still live long, happy, mostly healthy lives. Moreover, the stigma once attached to HIV has largely dissipated, as HIV-positive people have rejected victim-blaming and empowered themselves both in their medical treatment and in the respect and decency they demand from society. The Internet provides myriad resources for those living with the infection, and virtual support groups foster a sense of community. No one has to face HIV alone, and no one should feel ashamed about being HIV-positive. If I did have HIV, I decided, I would not let it destroy my life. But I would much rather not have HIV.

After 20 interminable minutes, no second red line showed up on my test—a negative result. My confusion grew deeper, though my spirits started to lift. I had now received one positive, one indeterminate, and one negative HIV test. I still didn’t like my odds. But the situation seemed slightly brighter than it had the night before. Six days later, I received mailed lab results from the urgent care clinic. Unbeknownst to me, they had run a highly sensitive immunoassay—and it was completely negative. My blood was not testing positive for HIV. The immediate sensation was not one of comfort, or even relief. It was bewilderment. Nothing that had happened to me seemed to make sense. And when it abruptly stopped happening, that made little sense, either.

Finally, more than two weeks later, my RNA test came back negative. Dr. Smith didn’t explain the delay—the test takes less than a week—nor did he attempt to explain his original misdiagnosis.

“I have no idea why the Western Blot was indeterminate,” he said. “But we should run one more immunoassay.”

He ran one more immunoassay. It came back negative.

In all, I received six HIV tests in the span of less than a month. Without insurance, the process would have cost more than $2,000; an RNA test alone is about $500. Had the recommendations of the Confirmatory Testing Laboratory, the Association of Public Health laboratories, and the Blood Products Advisory Committee been adopted more than a decade ago, I could have avoided the entire experience. My indeterminate test was the result of a lab error; nonviral Western Blots always are. For the foreseeable future, patients who receive nonviral Western Blots will be misdiagnosed. And like me, they will live, however briefly, with the belief that they have HIV.

I asked Bernard Branson, the associate director for HIV laboratory diagnostics at the CDC, whether he thought indeterminate results would ever disappear completely.

“No test is perfect,” he told me, “not even RNA tests.” The CDC is currently working to develop immunoassays that dramatically cut the rate of false positives, false negatives, and indeterminate results, but there may always be a few cases like mine, no matter how advanced the technology. It’s hard to know how many people get a false positive result. A 2005 study suggested a false positive rate from an immunoassay plus Western Blot of 1 in 250,000, but a lot of false positives are unreported, and the problem has not been the subject of much research.

“Why,” he asked me in return, “are you interested?”

I explained to him my own experiences, my week of anxiety, and my hope that others in my situation might not face the same difficulties I did. As I spoke, I felt some of the confusion, the fear, the trepidation of that awful week lurch back into my mind. I had received my final confirmatory test more than a month earlier, but the pall of HIV still hung over my life in an ineffable way. Even now, several months later, I wake up some mornings with the same sudden panic I felt the moment I got the call.

“How can something like this still happen?” I asked Branson. That, at heart, was the question that had been haunting me. I wanted an answer beyond biology, beyond virology, an explanation larger than lab mistakes and hasty diagnoses. I wanted that week of my life back, and if I couldn’t get it, I wanted to know why I lost it in the first place—why a widely used, highly sensitive test could malfunction, be misinterpreted, and bring me to the brink of despair.

Branson considered my question for a moment.

“How can it happen?” he said. “Bad luck.”

When I finished the interview, I scoured my room for all of the results I had received and tucked away during my month of HIV tests. Then I tore them up and threw them away.