Radiologists are making more errors when interpreting CT studies overnight than they are when examining scans in the daytime.

That’s according to researchers at Mayo Clinic, who found errors frequently occurred more in off-hour body CT interpretations examined overnight, and more so in the latter half of nighttime assignments. Radiologists were also found to have worse error rates at night compared to the day.

“The radiologists who were working overnight had schedules set up to give them ‘ample rest’," study author Dr. Maitray D. Patel, professor of radiology at Mayo Clinic Arizona, told HCB News. “They had 11 hours off before starting any assignment, and only worked a maximum of five nights in a row. The point is that someone has to read out the body CTs that occur after-hours, but are they susceptible to making more errors in doing that just because it is being done at night and they don’t always have a night schedule? Our study suggests that there is some impairment, even if they are well-rested for the night shift.”

Discrepancies affecting acute or follow-up clinical care were classified as errors. Daytime hours were between 7 a.m. and 5:59 p.m., while nighttime was between 6 p.m. and 6:59 a.m. The study did not look at the performance of radiologists when working Monday through Friday during regular hours and instead compared performance at night on any day to performance during the day only on weekends and holidays.

The team examined 10,090 body CT studies of the pelvis, abdomen or both, interpreted between July 2014 and June 2018. Scans were independently interpreted in-house and off-hours by radiologists who were part of a non-ACGME-accredited fellowship and were reviewed by an attending radiologist within 10 hours of initial interpretation, with the fellow interpretations submitted as complete final reports. Attending radiologists were specialists in body imaging, while the initial interpreting radiologists were fellows training in breast imaging (12 fellows), musculoskeletal imaging (eight fellows), or body MR (12 fellows).

Forty-four of the 2,195 studies examined in the day had errors, compared to 240 of 7,895 nighttime studies. Body CT interpretations during the day had an error rate of 2%, while those during the night had a rate of 3%. Thirty-two radiologists in all evaluated off-hour scans. Of these, 22 had higher error rates for night cases (69%). Errors in the last half of the night assignment were 125 out of 3,358 cases (12 a.m. to 6:59 a.m.), compared to the 115 found in the first half (6 p.m. to 11:59 p.m.) which consisted of 4,537 cases.

Of the 10,090 body CT studies, 9,610 were reviewed by attending physicians in the abdominal division. No difference in the error rate was found when evaluating this subset of cases, with 44 errors found in 2,164 day studies and 226 found in 7,446 night studies.

Patel notes that body CT studies are notoriously one of the types of studies in which more errors are made by non-specialists, and says one possible reason may be the function of the number of different organs that must be evaluated.

“One important note regarding our study is that the over-reads were conducted by specialists in body imaging,” he said, “whereas the initial interpretation was done by a generalist (someone who had not yet completed subspecialty training) — in that context, evidence shows that specialists often find additional observations or understand the relevance of observations that are “missed” by a generalist, by virtue of having more expertise.”

While he and his colleagues did not study the potential of any tactics for reducing errors, his personal recommendations include “using a checklist approach, taking notes during the review instead of just keeping a mental tally, make all observations before starting the dictation (instead of just dictating as you are evaluating, which is what we tend to do during the day), and read the dictated report before signing it off.”

The findings were published in Radiology.