Doctors Warn Women: Don’t Rely on Home Pregnancy Test

Over-the-counter pregnancy tests are touted in some cases as 99% accurate, but doctors say they are not as reliable as manufacturers claim.

Women who depend on the results, physicians say, could be endangering their lives.

Dr. Louise Tyrer, vice president for medical affairs at the Planned Parenthood Federation of America, is one of a growing number of health-care professionals who debate the value of the kits.

“The problem with using at-home tests is that most women are far too unaware of the potential risk of relying on those tests. Even if the test is negative, they could still have a tubal pregnancy,” Tyrer said.

Risk Called Considerable

That risk is considerable, she said, noting that the incidence of pregnancy outside the uterus, such as in a Fallopian tube, in the New York area is 1 in 80. A tubal pregnancy can cause severe internal bleeding, which can be fatal.

“If they have a negative test, that’s when they become complacent and say, ‘Well, I don’t have to worry about rushing out and doing anything now.’ But they could be endangering their lives,” Tyrer said.

If women get positive readings, she said, “Very often they say, ‘Oh well, I know I can’t get an appointment with a doctor and the first three months don’t matter.’ But we know they do. Nutritionally, it is the most important time.”

The 20 tests authorized for marketing by the Food and Drug Administration range in price from $6.50 to $15 and work on a color principle--changing the color of a testing fluid or testing stick if the hormone human chorionic gonadotropin is detected in urine. HCG is produced by the fetus.

Some home pregnancy tests are the so-called “ring tests” and are generally less expensive. They indicate the presence of HCG when a ring or band of color is detectable on the test tube.

“We made a statement in 1980 that the most accurate kind of (at-home) pregnancy test is the monoclonal antibody test. But the less-sensitive ring tests have false negative rates that vary from 1 to 30%,” Tyrer said.

Dr. Ernest Scher, a Maryland obstetrician, said he sees at least one patient almost every day who has had a false reading from the home pregnancy test. In most cases, he said, patients do not follow the directions as closely as is required and false negatives or positives result.

But the doctor said that makes sense because his patients are not laboratory technicians trained to conduct tests and analyze data, and most bathrooms are not equipped with timers and temperature controls.

In early February, Scher had a patient who had taken an at-home pregnancy test on a Tuesday morning that showed a bright blue, indicating the presence of HCG hormone, or pregnancy. But that afternoon, she began to bleed.

Pregnancy Mimicked

After being examined by two doctors, including Scher, and based on the test results the previous day, the doctors concluded an immediate dilation and curettage were necessary to prevent hemorrhaging because all indications pointed to a miscarriage.

But nearly $1,000 and 10 days later, a pathology report on the supposed “miscarriage” picked up no placental tissue. Scher concluded she had simply had an estrogen buildup that mimicked a pregnancy.

“I thought because the test said it was 99% accurate I could trust the results. I really thought I was pregnant,” the patient said.

“The tendency is for people to assume they have a diagnosis (after taking the test). Either ‘I am pregnant’ or ‘I am not pregnant,’ but you cannot diagnose pregnancy based on the tests. It distorts the purpose of the tests and gives misinformation to consumers,” Tyrer said.

In 1976, the FDA approved the first test, e.p.t., which is produced by Warner-Lambert Co., on a “grandfather clause” under which the test was not subjected to the same analysis a new product would undergo because it was “substantially equivalent” to tests existing prior to 1976 for physician or laboratory use, said David Duarte, an FDA spokesman.

The tests that followed e.p.t. onto the market were permitted to be sold to consumers under the same clause, he said.

“Sponsors submitted data that was balanced to prove it’s effective, and the reviewers know the science behind the device,” Duarte said. “The standard is that they (the tests) have to be as accurate as a laboratory test and that you have to follow directions correctly.”

Harry Jonas, president of the American College of Obstetrics and Gynecology, has determined that the tests are “generally accurate,” but “must be done exactly as instructions indicate,” a spokesman for the group said, adding that Jonas stressed the word “exactly.”

But that is where the problems arise, doctors say.

Too often, patients are not sure when they should have menstruated and consequently use the tests, which some manufacturers claim are effective as early as one day after a missed menstrual period, too soon.

“The tests are not accurate for early testing, and you can get false negatives because they are not sensitive enough,” said Dr. Marian Damewood, director of Johns Hopkins Hospital’s in-vitro fertilization program.

‘Relieves Anxiety’

“We can do in-office testing that is less expensive and will be done at the correct time of month to produce a more accurate result. It relieves a lot of needless anxiety,” she said.

Marlene Walker, a nurse practitioner who screens patients at Hopkins’ obstetrics department, said the tests are almost always accurate when she sees patients who are six or seven weeks pregnant.

“Almost to a one they ask me to redo the tests because they don’t trust their own eyes or their expertise,” she said, adding that the office tests usually concur with the at-home results.

But Walker said she does not believe the tests are as sensitive early in the pregnancy.

“They’re assuming every woman in the world has a 28-day cycle,” she said. “That’s just not true. Anything can throw a woman off, no matter how regular she is.”

Walker also said she thinks television commercials that imply the products are foolproof as early as one day after a missed menstrual period are misleading.

“The one that is on television that says, ‘Yes, darling, of course I’m sure.’ I hate that one,” she said. “I tell my patients to wait (before taking the tests). If it’s a pregnancy, you get to keep the kid forever, so one more week won’t hurt.”

Mary Doshi, a researcher at the University of Wisconsin, published a study of the ring-method tests in the American Journal of Public Health in May, 1986, while working at Marquette University’s program in medical technology.

Doshi found that many inaccuracies in test results were caused by the tests’ lack of sensitivity in the early stages of pregnancy.

In her experiments she divided the urine of 109 women, taking half into the laboratory and giving the other half to the volunteers to test at home.

Lower Accuracy Rate

Doshi said in the laboratory, using the same tests the women used in their homes, she came up with an average of 92% accuracy for the tests. The non-professional testers achieved an accuracy rate of between 45.7% to 89.1%.

“The manufacturers urge women to test as early as six days after the expected menses. However, the sensitivity of these kits was demonstrated to be inadequate 27% of the time for early detection,” Doshi wrote. “Manufacturers should be encouraged to re-evaluate their claims.”

The FDA approved the kits based on data from manufacturers that the kits are 97.4% accurate.

A spokesman for Warner Lambert defended his company’s pregnancy testing product and its accuracy claims. He insisted that the manufacturer advertises the product as an indicator of pregnancy and not a diagnosis.

“We don’t call these diagnostic tests. None of them should substitute for medical care,” said Warner’s spokesman Marshall Molloy, adding that the company does not want the tests kept on store shelves near diagnostic products.

But Lora Queller, a spokeswoman for Ortho Pharmaceutical Corp., which makes three over-the-counter pregnancy tests and advertises one of its products as “the easy way to know for sure,” said: “Ortho likes to see them next to diagnostics. They don’t want it to be seen as another tampon box.”

Instructions in the tests indicate that a woman who gets a negative result and does not begin menstruating within a week should take the test again. If the result is still negative, the woman is advised to see her doctor.

Dr. David Nagey of the University of Maryland Hospital said he uses the negative and positive results to help him time a woman’s pregnancy.

Use Encouraged

Nagey said he encourages medical students to recommend the at-home predictors to their future patients.

“A lot of times, women don’t ovulate regularly, and it’s difficult to know when they got pregnant. If they tell me, ‘This week the test was negative’ and the next week it’s positive, it can help us gauge when she got pregnant,” he said.

Doshi, who is working on a study of the monoclonal antibody tests, agreed that the new tests are better than ring tests, whose accuracy can be disturbed by vibrations, soap, temperature and foreign particles. But she said the new tests continue to be less fail-safe than the firms would lead the consumer to believe.

Doshi said that the monoclonal antibody tests are temperature-sensitive and that timing is crucial to the test’s accuracy. She also cautioned that the human factor can cause an inaccurate reading aside from any problems with the test.

“Remember, the women are interpreting their own tests. If they have any kind of interest in the result, you can see into it what you want,” she said. “You can see any shade of red, blue, pink or clear depending upon whether or not you want to be pregnant.

“It is the same principle as doctors treating themselves or their families. That is why they don’t do it.”