VOLUME 46 | NUMBER 2 | APRIL 2011
Commentary on Sharek: Adverse Events and Errors - Important to Differentiate and Difficult to Measure
The paper by Sharek and colleagues in this issue of Health Services Research describes some of the characteristics of a method of measuring adverse events in hospitalized patients. The method was developed by the Institute for Healthcare Improvement (IHI) and is referred to in the paper by Sharek and colleagues as the IHI global trigger tool. This paper presents a large and well-designed reliability study and as such is an important contribution to the field of patient safety.
Reliability quantifies the reproducibility of a measurement technique, which is a key piece of information. For example, in this case, it would allow one to calculate how many observations per facility are necessary to generate an acceptably precise estimate of its adverse event rate. This paper does not provide evidence about validity, another measurement characteristic that describes how well the measurement captures the underlying construct.
An important point is that the reliability estimate presented in the Sharek and colleagues' study is not a characteristic of the IHI trigger tool itself. Reliability is a function of the entire measurement process, which includes the precision of the instrument, the measurement procedure or method of applying the instrument, and the amount of variability of the true adverse event rate in the underlying population. In order to infer that one will obtain the same level of reproducibility as is reported in the Sharek and colleagues' paper when using the instrument in another setting, one has to use the instrument with a similar measurement procedure and population. The broadly representative sample of hospitals included in the study by Sharek and colleagues is a strength that makes the reliability estimates more generalizable.
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