Confirmatory testing reduces risk

Q We recently had a physician tell us that we need to do a confirmatory
culture on all negative rapid strep tests. Do we put the lab at risk if
we do not?

A The risk here is more likely to fall on the physician
who chooses not to follow up the screening test by ordering a culture.
The example, however, is a good one for examining the need for
second-level confirmatory testing in the lab setting, because the
principles are the same.

From a risk-management standpoint, determining
whether to do a second-level test when a screening test is negative
hinges primarily on two points: 1) the sensitivity and specificity of
the screening test (and the confirmatory test) and 2) the seriousness of
a false positive. Develop a policy with these points in mind.

The effectiveness of a screening test in sorting out
positive results from negative results is critical. Some screening tests
have a high incidence of false positives, making them less useful for
initiating treatment, especially if the treatment is expensive or
potentially toxic. The incidence of false-positive results in HIV
testing, for example, has been an issue since the earliest tests were
designed and, for some methods such as the oral rapid-screening test,
remains an issue. The higher the incidence of false positives, the
greater the need for confirmatory testing before instituting treatment.

Similarly, the ability of a test to definitively
rule out
a diagnosis becomes important when the risk of failing to
make a diagnosis is greater. Troponin testing, for example, has proven
valuable because its false-negative rate is low. Fewer than 1.5% of
patients with a negative troponin go on to have a myocardial infarction
within 30 days of testing — a pretty good track record. When determining
policy about follow-up testing, performing an assessment of a screening
test as part of the overall risk analysis is an important step.

The ultimate danger to the patient of a false result is
also essential to the risk assessment. Often, a rare result is dismissed
from consideration because it is rare. If the result is devastating,
however, the balance of risks changes. Remember the Challenger explosion?
Physicist Richard Feynman pointed out in the hearings that the risks of
O-ring deformity were dismissed because they were rare — but the results
were catastrophic. Rare does not mean insignificant.

The higher the incidence of false positives, the greater the need for confirmatory testing before
instituting treatment.

A problem arises when a variance exists between the
standards advocated by experts and those actually followed in the community.
There may be good reasons for deviating from the recommendations of a
professional body, but there are also legal risks. An institution that
deviates from the published standard gives an attorney a foothold in filing
suits and makes it easier for him to find an expert in support of a lawsuit.

Part of the decision-making process is to balance all the
risks, including the risks to patients, individually and as a group, of
failing to follow up with a confirmatory test. In the case of strep testing,
rheumatic fever may be rare, but its incidence is 100% for the patient who
experiences it. Rheumatic fever is a serious medical problem and is the sort
of complication that is likely to give rise to a lawsuit. Once that happens,
the “battle of experts” will actually end up determining what standard
actually applies.

The issue of performing follow-up tests came up in a
lawsuit against a family practitioner who did not order a confirmatory
culture on a child with a negative strep test. The child later developed
rheumatic fever, and his family sued the doctor — but lost. The physician’s
medical expert, Paul Fischer, MD, wrote an article about the experience and
gave a convincing medical argument for not performing a confirmatory
culture in these circumstances. The article, “Defending the Real Standard of
Care,” can be found in Family Practice Management; 2008;15(2):48 or
online through Medscape.

Making an argument about the sensitivity of tests, the
costs and risks of antibiotics, the relative difficulty and unreliability of
cultures themselves, and the community standard of practice carried the day
in Dr. Fischer’s case, but the outcome is never guaranteed when a jury is
involved. Some institutions put more weight on avoiding the potential for
litigation when weighing the costs and risks of not doing additional
testing. The costs to the institution of doing additional tests to back up a
false-negative test may not be much greater than the costs of a single
lawsuit, even if the institution prevails in court.

If your practice is to vary from published expert standards, do your
homework and make a clear, detailed case for why the standard is not
applicable to your particular situation. Document a basis for developing
a more reasonable policy for your institution. Regularly assess the
policies to make certain they take into account changes in recommended
practices and available technology. Sound decisions based on good
science and good sense can keep the case out of court or be the basis
for a winning argument if it does go to court.

Barbara Harty-Golder is a pathologist-attorney
consultant in Chattanooga, TN. She maintains a law practice with a
special interest in medical law. She writes and lectures extensively on
healthcare law, risk management, and human resource management.

MLO’s “Liability and the Lab”is intended
to provide risk management and human resource management education; it
is not intended to provide specific legal advice. If you require legal
advice, the services of an attorney should be sought. Dr. Harty-Golder
welcomes your questions, which can be sent to her at
[email protected]
Unless otherwise noted as “confidential”
by readers, all queries will be considered for publication without
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