Disputes Because of Differences in Indicator Data
On occasion, we receive telephone calls from a head nurse worried about discrepancies in data: she
is obliged to put in performance figures for her department for the month and uses the [Statistics Overview]
put out by the Medical Records department; however, she found indicators on our website with apparently
the same name but different figures. Since performance results directly affect her own and her members' salaries, she is
very concerned about which set of data to use — usually expressed as "which data is correct?"
Convince By Reasoning
Look at the diagram above. The dotted vertical lines separate months (July to November) and the horizontal lines
represent patients (A~F). each of whom was admitted and discharged from the hospital as indicated by the length of
the horizontal line. The numbers above the lines indicate the days that the patient was an inpatient for that month:
for example, patient A was admitted on August 11 and was an inpatient for 20 days during August, the full month
of September (30 days), and a further 22 days in October, at which time he was discharged from hospital. His total
length of stay (LOS) was 72 days, as indicated in the table on the right.
The push-pins represent an event being studied (such as patient falls, hospital-acquired infections, or invasive
procedures such as CVP and CPR). For this instance, let us say that each push-pin represents one activation of
the rapid response team (RRT) for an unstable patient. Patient A, therefore, had the RRT activated a total of 3 times,
one of which was during the month of September.
Buainess (performance) Indicators
The blue background indicates the month of September, which is the month which the head nurse must supply
performance data for. The Medical Records department supplied a figure of 3 activations for 5 patients (A, B, C, D, F) for that
ward in September.The combined patient-days for those patients that month was 30 + 18 + 10 + 21 + 28 = 107 days, giving an
activation rate of 3 ÷ 107 = 28.04‰, a risk
[1] of 3 ÷ 5 = 60%.
Quality Indicators
Since RRT monitors the success of early activation in preventing deterioration, CPR, and death, the denominator is
restricted to patients for whom all results are known; that is, those that have been discharged from hospital during that
month. Moreover, since it is an indicator measuring the quality of care provided, it is patient-centered and covers the
entire course of the patient from admission to discharge. Hence, for the month of September, 3 patients (B, C, D) were
discharged. For quality indicators, the event being studied must be restricted to the patients in the denominator in
able to discuss causality, incidence, and whether quality improvement initiatives are having any success. For the 3
patients discharged in September, there was a total of 2 activations (B, D) of the RRT during a total of 18 + (14 + 10) + (19 + 31 + 21) = 113 days
of hospital care = 2 ÷ 113 = 17.7‰, a risk
[1] of 2 ÷ 3 = 66%.
Suddenly see the Light!
Aha! so there is no mistake in the data or the calculations. It is because the goals are different, hence the indicators
are defined differently. Both are valid. Business indicators tend to be used for monitoring process, quality indicators
tend to be used for assessing outcomes. The head nurse should use the first type for replying to questions about
performance (viz work load and efficiency), but the second type when assessing quality improvement projects
(such as quality control circles, root cause analysis etc) within her department.
Definitions
- Risk: probability of occurrence of a given event. Calculated as:
Risk = (number of events) ÷ (number of people at risk)
Reference: Pereira-Maxwell F. 1998 A-Z of Medical Statistics: a companion for critical appraisal.p.72
Gray Publishing, Tunbridge Wells, Kent.