Factors Identified That Can Lead to False-Positive Mammograms
WESTPORT, CT (Reuters Health) Oct 18 - A review of the medical records of 2227 women who received between
one and nine mammograms over a 10-year period has revealed four patient variables and three radiologic variables
that independently affect the chances of a false-positive result on screening mammography.
Dr. Cindy L. Christiansen, of Boston University, and colleagues report that during the study period, 6.5% of 9747
screening mammograms were false-positive and 23.8% of all the women had at least one false-positive mammogram.
According to the data, the risk of a false-positive mammogram decreases with increasing age and increases with the
number of breast biopsies performed, a family history of breast cancer and current or past use of estrogen. A
women currently using estrogen had about a 29% increase in risk over a women not using estrogen, according their
report the October 18th Journal of the National Cancer Institute.
Procedural characteristics that increase the risk of a false-positive result include longer time between mammograms
and not comparing the mammogram to the previous one. When a mammogram is not compared to a previous mammogram,
the risk of a false-positive increases by 74%, the data show.
Also, the radiologist who reads the film can decrease or increase the likelihood of a false-positive result. Among the
93 radiologists included in the study, about half had false-positive rates of <5%, about one quarter had rates
between 5% and 10% and another quarter had rates >10%.
"The cumulative risk of a false-positive mammogram over time varies substantially, depending on a woman's own risk
profile and on several factors related to radiologic screening," Dr. Christiansen's group concludes.
"For the average woman in our study, there was a 43% chance (more than 4 out of 10 women) of having a
false-positive mammogram by the ninth mammogram," Dr. Christiansen told Reuters Health. "Women may receive 30 or
more mammograms in a lifetime and this cumulative risk rises as the number of mammograms increases."
The researchers believe it may be possible to develop an equation to predict a woman's risk of receiving a
false-positive result on screening mammography. "We hope this study will serve to educate women about their risk of
a false-positive, reduce their anxiety when a mammogram requires special follow-up, and will encourage women to
discuss false-positive risks with their doctor and radiologist," Dr. Christiansen told Reuters Health.
J Natl Cancer Inst 2000;92:1657-1666. |
