Intermountain Healthcare hospitals use a single, standardized laboratory and automated testing process for estrogen receptor/progesterone receptor (ER/PR) tests to minimize testing errors.
To test the (1) variability in ER/PR negativity among hospitals and (2) association between specimen handling conditions and ER/PR negativity.
Retrospective study of women who had breast cancer surgery at 7 Intermountain hospitals and ER/PR tests ordered between 1997 and 2003. Data were extracted from cancer registry. Frequency of ER/PR negativity was calculated for each surgery day and compared among hospitals and between 2 groups: regular (specimens obtained Sunday through Thursday, more likely to be tested within 24 hours of surgery) and prolonged (specimens obtained on Friday and Saturday, more likely to be tested more than 24 hours after surgery) specimen handling conditions.
Five thousand seventy-seven women were tested for ER/PR. The frequency of ER and PR negativity was 20.9% and 27.9%, respectively. It increased with each day of the week for both ER (P = .03) and PR (P = .059) and tended to be higher for prolonged specimens for ER (23.6% versus 20.4%; P = .03) and for PR (30.1% versus 27.4%; P = .11) compared with regular specimens. After controlling for age and tumor size, both ER (P = .02) and PR (P = .02) negativity was significantly different among the hospitals and was associated with prolonged specimens for ER (P = .04) but not for PR (P = .09).
Estrogen receptor and PR negativity remained highly variable among hospitals despite use of a single laboratory and tended to be significantly associated with prolonged specimen handling. More studies are needed to confirm these findings.