Pap Smears, False Negatives & Cancer


A typical scenario preceding Pap smear litigation
involves a false-negative and/or unsatisfactory smear
"discovered" upon review of prior negatives from a
woman with cervical carcinoma. A College of American
Pathologists (CAP) Q-Probes study on the five-year "look
back" rescreening of prior negatives following the
diagnosis of high-grade carcinoma (HSIL) found 10
percent of the prior smears to be false-negative for
squamous intraepithelial lesion (SIL)/carcinoma. The
proportion of false-negatives rose to 20 percent when
atypical squamous cells of undetermined significance
(ASCUS) were included.

The American Cancer Society predicted 15,700 new
cases of cervical carcinoma in 1996, and studies
indicate that 60 percent to 75 percent of women dying
of cervical carcinoma have never had a Pap smear or
they did not have one in the prior five years.
Assuming that 40 percent of the women representing
new cases of cervical carcinoma have a single Pap
smear in the prior five years and a 20 percent false-
negative rate discovered on rescreening prior negatives,
there is potential for a minimum of 1,256 new claims in
1996 for failure to diagnose cervical carcinoma.

Annual Pap Smears are Important

The success of the Pap smear as a screening test for
cervical cancer detection is largely responsible for the
70 percent decline in deaths from cervical cancer that
has occurred over the past 50 years. No screening test,
however, has 100 percent sensitivity, and while there is
a wide range in the reported false-negative rate for a
single Pap smear, 15 percent to 25 percent is widely
accepted. Sampling false-negatives (absence of
abnormal cells on the smear) are slightly more common
than laboratory false-negatives, which are divided about
evenly between screening errors and interpretation
errors. There is agreement that the lowest laboratory
false-negative rate that can be achieved by manual
screening is five percent, and that the average
laboratory false-negative rate is probably about 15
percent. Every laboratory has a false-negative rate,
including those supervised by experts. Low-grade
squamous intraepithelial lesion (LSIL) accounts for most
false-negatives, and about half of these regress. For
those that progress, evolution is usually slow, and thus
the consequences of a false-negative are minimized by
an annual Pap smear. Twenty percent to 30 percent of
women with LSIL on Pap smear, however, will have
HSIL on biopsy.


Managed Care Concerns

The effect of managed care on Pap smear liability raises
additional concerns. Will the trend toward
regionalization of laboratory services interfere with
pathologist-physician communication or with follow-up
cytologic/histologic correlation? Will patients' frequent
change of doctors and health plans interfere with
appropriate Pap smear follow-up? What will be the
impact as responsibility for collecting Pap smears and
following up on abnormal smears shifts from
gynecologists to primary care physicians? Studies show
that only 75 percent of family physicians and 50 percent
of internists do routine annual Pap smears. But
recommendation of an annual Pap smear is required just
to ensure that a Pap smear is obtained every two to
three years. Will the frequency of routine Pap smears
be further reduced by the pressures of cost
containment-and will this diminish the opportunity to
detect lesions "missed" on prior false-negative Pap
smears?

Thorough Review of the Basics of Cervical Cancer...
http://www.emedicine.com/radio/topic140.htm