Implementation of Clinical Decision Support Rules to Reduce Repeat Measurement of Serum Ionized Calcium, Serum Magnesium, and N-Terminal Pro-B-Type Natriuretic Peptide in Intensive Care Unit Inpatients

Discussion

We implemented “soft-stop” CDS rules for iCa, Mg, and NT-proBNP, using pop-up alerts that could be overridden electronically by the ordering provider. We achieved a 48% decrease in iCa, 39% decrease in Mg, and 28% decrease in NT-proBNP testing in the 90-day period immediately after implementation, which was sustained over the subsequent 90-day period. Order entry interventions have been described previously for iCa, Mg, and NT-proBNP (18–20) and other commonly ordered laboratory tests (18–22), although both our methods and results differed from strategies previously described.

One academic medical center decreased iCa orders by approximately 75% by establishing a reflex calcium test, such that iCa was performed only when total serum calcium was <8.0 mg/dL or >10.2 mg/dL. Direct (without the total calcium reflex) iCa orders were still allowed, but only by special request (18). We chose not to pursue this strategy, primarily because iCa is ordered approximately 3 times more often than total calcium in our ICU practice. Thus, introducing a reflex iCa process may have inadvertently increased our total calcium testing. Our results demonstrate that significant improvement (48%–54% reduction) in iCa utilization can be achieved without performing reflex testing.

A CDS rule aimed at reducing repeat BNP ordering in a community hospital resulted in an approximately 21% reduction in BNP testing across all inpatient areas in the 3 months after the CDS rule intervention (19). In that intervention providers were not required to enter a reason or indication for repeat ordering. Despite this, the observed decrease in testing was similar to what we observed with our CDS pop-up alert that required an indication for repeat testing (23%–27% decrease).

Another institution addressed utilization of iCa, Mg, and Phos by creating an order entry pop-up that addressed all 3 tests on the same alert (20). In the first phase of this study, orders placed for Mg tests occurring more than 72 h into the future were flagged, resulting in a 29% decrease in weekly Mg orders. In the second phase, recent magnesium, calcium, and Phos test results were presented to the ordering provider along with education regarding appropriate indications for testing. Testing was also limited to once per order (no future order entry). This resulted in a paradoxical increase in serum Mg orders. Finally, in the third phase they targeted only magnesium, displayed recent results, limited testing to once per order, provided education regarding appropriate indications for testing, and required users to select an indication. This resulted in a 51% decrease in weekly Mg orders. Our intervention also included recent serum Mg results and education on appropriate test use, and required an indication for repeat testing. We achieved a 39%–49% decrease in Mg orders, similar to the results in phase 3 of the aforementioned study, but without limiting future order entry.

The effectiveness of soft-stop CDS rules remains controversial. A recent study of a soft CDS intervention on repeat troponin orders (outside of the defined serial troponin panel) demonstrated no impact on troponin ordering (21). Another study compared a “hard-stop” CDS rule (phone call necessary to override) vs soft-stop rule for duplicate laboratory orders placed on the same day of an inpatient stay. This study found that the soft CDS rule reduced duplicate testing by only 42.6%, compared to 92.3% for the hard stop (22). However this intervention was aimed only at duplicate tests ordered on the same day of service, rather than testing commonly repeated over multiple days of an inpatient stay (22). Because our intervention included specific tests (e.g., iCa and Mg) that require repeat measurement for some patients, a hard-stop approach would not have been appropriate.

We found that soft-stop CDS rules had a significant impact on test ordering in the pilot ICU areas. Although the overall monthly number of tests avoided (approximately 1400) is similar to the monthly volume of CDS pop-up alerts triggered (approximately 1000–1100), the override rate of approximately 66% suggests that the CDS pop-up alert alone was not responsible for the reduction in test volume. The unanticipated decrease in Phos testing during the same time period suggests that implementation of the CDS rules resulted in a change in test ordering patterns in the ICU. The decrease in pop-up alert volumes during the first 3 months of the intervention also suggests that providers changed test ordering patterns to avoid interacting with the CDS pop-up alert box.

There were many more pop-up alerts and overrides for Mg compared to iCa or NT-proBNP, suggesting that providers were less willing to change ordering patterns for Mg. However, the immediate and sustained decrease in Mg testing volumes (Fig. 1) after CDS implementation demonstrates that the Mg CDS rule was still effective. The increase in pop-ups and overrides (predominantly for serum Mg) during the last 3 months of the intervention may have resulted from inadequately sustained educational efforts as new residents and fellows entered the practice, less outcome-based evidence to support a more conservative Mg replacement strategy (compared to calcium replacement), or other factors.

One limitation to our pop-up alert is that indications were entered in a free text field, such that indications not defined in the rule could be used to proceed with testing. Another limitation to our CDS rule is that it did not directly prevent future order entry (e.g., daily Mg or iCa orders for several days). Future or advance order entry for the duration of an ICU stay is very uncommon in our practice. In environments where future order entry is commonly performed at ICU admission for the duration of an ICU stay, a CDS rule that prohibits or addresses future order entry may be needed to achieve similar results. However, the concepts used in our intervention would still apply, with many CDS systems supporting a rule limiting future order entry.

Different outcomes described for soft-stop CDS rules may reflect differences in the nature of the tests targeted (troponin vs electrolytes), differences in the design of the CDS pop-up alert (difficulty to override the screen, requirement for defined indications vs free text field), differences in institutional culture, or other variables. Despite the high override rate of pop-up alerts (predominantly for Mg), significant reductions in testing volumes were maintained throughout the intervention period.

Decreasing the frequency of testing and associated costs does not result in improved quality of care if patients are experiencing adverse effects as a result of the decrease in testing. To ensure that this was not the case in our patient population, we searched for ICD-9 codes associated with arrhythmias, tetany, electrolyte-related seizures, and hypocalcemia. We did not observe any change in the incidence of these conditions nor receive any feedback from clinicians with concerns that this utilization initiative harmed patients.

In summary, we implemented CDS rules with soft stops in 5 ICU areas, to decrease unnecessary repeat testing of iCa, Mg, and NT-proBNP. Our approach resulted in decreased testing of each of these analytes, along with decreased testing costs, and no increase in adverse patient outcomes. In the future, we will expand the number of inpatient care areas with order entry CDS rules for iCa, Mg, and NT-proBNP, as well as create repeat order rules for additional high volume tests.