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Home Test Kits ::
Directions For Use Guidance
Home Diagnostics Directions
It may seem obvious but make sure that you follow the directions carefully on any kits that you buy. Home
test kits, for the most part, involve relatively simple procedures. Some are as straightforward as one
pregnancy test in which chemically treated test strips dipped in urine produce colored indicator lines.
Others require a finger prick and the placement of a blood sample onto a reagent strip. The strip is
inserted into a machine that measures blood glucose levels.
Still others, like the only FDA-cleared HIV home sample
collection kit, consist of multiple components, ranging from pre-test counseling information to a personal
identification number for obtaining the test's results. In any case, the FDA requires that the kits be
simple enough for an average consumer to use at home without a doctor's supervision.
Some home tests give their results as positive or negative. Performance of these is described in terms of
sensitivity--the probability that the results will be positive when a disease or condition is present; and
specificity--the probability that the results will be negative when a disease or condition is not present.
Other home tests give numerical results. Performance of these is described in terms of precision--how
reproducible the results are when a test is run over and over; and accuracy--how well the results compare
to a laboratory test. All diagnostic tests have limitations, and sometimes their use may produce erroneous
or questionable results. Test results obtained at home can often be clarified by a physician, who may
recommend another test that is handled by a laboratory.
Home test kits should not be stored in places where they might be exposed to extreme temperatures, since
this may cause product deterioration over time. He also stresses the importance of checking test-kit
expiration dates--chemicals in an outdated test may no longer work properly, so the results are not likely
to be valid.
While manufacturers of professional test kits used in clinics and hospitals or doctor's offices are
required to include sensitivity and specificity information in their labeling, the FDA does not make
manufacturers of home test kits do so. But Lori Moore of Maysville, Ky., thinks they should.
"As a consumer, I want to see the data that supports this being a good brand," she says. "For the average
person, this information truly lets them know what they're purchasing." But Moore happens to be more
familiar with sensitivity and related product information than most people, since she has worked as a
registered laboratory technician. Still, she insists that today's consumer wants more information visible
on the product's label than is currently available.
Dave Lyle, a medical technologist in the FDA's clinical laboratory devices division, explains that "the
decision was made several years ago to exclude this information from over-the-counter kits because it might
confuse the consumer." However, Lyle agrees that "in today's world, most consumers are very sophisticated
and want as much information as possible to make an informed decision."
Complications of home testing may interfere with obtaining accurate results. Consumers may not be able to
follow the instructions. Proper collection, storage and shipment of specimens are all critical for
accuracy. Samples held too long, for example, or subjected to severe temperature changes could generate
false positive or negative readings. Urine samples taken too early or too late in the day or foods eaten
that mimic the metabolites being measured also can produce inaccurate readings.
And people need to beware of bogus tests, those not cleared by the FDA. Unapproved home test kits do not
come with any guarantee of accuracy or sensitivity, nor do they have a documented history of dependability.
Proper training to interpret results is not provided with the kits, and they do not have a validated record
of precision. This means that unapproved tests may be inconsistent and inaccurate.
Approved tests, on the other hand, have undergone extensive study and review by the manufacturer of the
product to satisfy the FDA's requirement that they are as safe and accurate for consumer use as their
laboratory counterparts are for professional use. For any in-home test, the manufacturer must convince the
FDA that the results of a test will benefit consumers and that consumers have the knowledge necessary to
decide whether testing themselves is appropriate.
For example, Stewart says people purchasing blood pressure monitors should look for a statement in the
label that says the device has been validated in a human study "where the statistics have been calculated
to ensure that good accuracy can be demonstrated." Stewart says the label also should include a statement
that says measurements obtained by the blood pressure monitor are equivalent to those obtained by a trained
observer using a cuff and stethoscope.
"Indeed, reading the label is the most important thing," he says, "but it might also be useful to ask the
pharmacist or one's doctor to get a recommendation."
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