‘Lockout rules’ have been proposed for inpatient blood testing in hospitals to stop medical staff inappropriately ordering repeat tests after normal ones “just to keep an eye on things”.

In a study of how to apply Quality Use of Pathology principles to wasteful pathology testing, researchers in NSW analysed the re-ordering patterns and outcomes for full blood count (FBC) and urea and creatinine (EUC) tests in two hospitals.

The two tests accounted for over 90% of all inpatient pathology requests for mainstream pathology  tests performed daily in the John Hunter Hospital in Newcastle.

A review of test ordering over a two year period found that a total of 122,733 FBC test sets were ordered at the hospital. Between 40–45% of inpatients had FBC and/or EUC on any given day, and of these tests, 26% were normal, 70% were abnormal and 4% were very abnormal. The majority (62%) of repeat tests were normal when the prior test was normal.

The time interval for retesting (second test) for FBC was longer after a normal test (47 hours) than after an abnormal test (35 hours) or a very abnormal test (21 hours).

Over time, the retest interval for abnormal and very abnormal tests tended to go to 24 hours, i.e., routine ordering on a daily basis.

The retest interval for FBC after a previous normal result tended to stay at 48 hours rather than regress toward 24 hours.

Based on the retesting results and time intervals, the researchers estimated that a ‘lockout’ policy on ordering FBC after a previously normal test of 12 hours would eliminate only 0.2% of tests at the hospital over 2 years. A lockout of 48 hours would eliminate 2.6% of tests without missing a single very abnormal test.

The combination of a 12 hour minimum retest interval paired with a 48 hour lockout would increases the number of FBC tests prevented at the hospitals to 7% of all FBC tests, at the expense  of missing 0.2% (n=20) very abnormal results.

And since the cost of an FBC test is AU$16.95, the 48 hour lockout would potentially lead to the 500-bed hospital saving over $144,000 in FBC tests, over 2 years, equivalent to $400/bed/year.

“These data suggest that after the first 2 or 3 inpatient days, staff are ordering pathology tests routinely every 24 hours regardless of the previous value,” the study authors said.

They noted that previous research had shown that most pathology ordering is performed by junior staff (interns and junior registrars), with the most common reasons reported by residents for ordering tests being: habit (90%), lack of knowledge of costs (86%), diagnostic uncertainty (82%), and fear of embarrassment (76%).“Our results suggest a potential novel approach of ‘hard-wiring’ or at least flagging evidence-based lockouts in a computerised physician order entry system, based on the results and timing of the previous test.

We suggest applying a lockout (potentially 48 hours) to EUC and FBC orders where the default value is the cancellation of the test but the ordering physician is able to override this to allow for clinician judgement.

“This ‘nudge’, i.e., moving from ignoring the alert to having to override the alert, may be sufficient to shift ordering behaviour,” they concluded.

The findings are published in Pathology.