Saturday, February 11, 2006

The dangers of overtesting

One of my patients who had conceived after taking IVF treatment at our clinic came to me in tears. She had registered with an obstetrician, who had performed a "routine" "triple marker test" to screen for birth defects. This is a simple blood test, which was first introduced for screening older women who were at increased risk for having a baby with Down's syndrome ( trisomy 21) , and is done at 16 weeks of pregnancy. However, since it's such an easy test to do, many doctors now do it routinely for all their pregnant patients. The blood test measures the levels of 3 hormones - HCG, AFP ( alpha fetoprotein) and estriol. These levels are then mathematically manipulated, to give a risk figure.
She was only 28 years old, which meant that her risk of having a baby with Down's syndrome was very low to begin with - less than 1 in a 1000. It's not a good idea to perform screening tests when the prevalence of the disease being screened for is low, because the chance of getting "false positives" ( abnormal results in a healthy patient) are very high.
When her results came back, her doctor told her that her AFP level was low , which meant that her baby did have a chance of having Down's syndrome, even though this was small; and the only way of ruling this out was by doing a "minor procedure" called an amniocentesis, in which amniotic fluid is sent for genetic testing.
Since patients are so worried about having an "abnormal" baby, most are willing to go to any length to ensure their baby is normal. They are quite happy to blindly follow their doctor's advise - after all, " the doctor knows best " , doesn't she ?
However, she wanted a second opinion, since this was an IVF pregnancy, and came to me for a second opinion. ( Once you become senior, you become a doctor's doctor !)
I sat down with her and explained her results to her. Her HCG and estriol levels were in the normal range and the AFP was marginally lower than normal . The computer calculation showed her levels were well in the normal range, and her re-calculated risk of having Down's syndrome was actually re-computed to be even lower than expected - only 1 in 2000. This should have been very reassuring, and should have set her mind at peace. However, her doctor did not take the trouble to explain the test results to her - and seemed to use the triple test as an excuse to do even more ( expensive and remunerative !) testing.
Don't doctors see the harm they are doing by medicalising pregnancy ? They are converting a healthy event to a "high-stress" medical journey, littered with hazards and risks ! Instead of enjoying her pregnancy, this woman is petrified that her baby is going to be abnormal ! No matter how much I tried, I could not reassure her, and she plans to go ahead with the amniocentesis.
Most probably the procedure will be eventful - and since all's well that end's well, she'll forget all about this. However, the risk of miscarrying a healthy baby after an amniocentesis ( even in the best of hands) is 1% - and I pray that she doesn't fall into that 1% !

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