What to know
There are various approaches to quality assurance, some better than others. Monitoring classification levels concurrently can be accomplished by adding quality assurance or calibration radiographs with known classifications to a set of radiographs with unknown classifications. This is done without the reader being aware which are the calibration radiographs.
Quality assurance radiographs
Quality assurance radiographs should include a range of abnormality levels and types previously classified by expert readers. The benefits to this approach include:
-The reader is under pressure to conform to standard classification practices. This is because the reader is unaware of which are quality control radiographs but knows that they exist within the study.
-The results for the quality assurance radiographs can be used to assess the accuracy of the reader's classifications. Based on this assessment, it may be necessary to disregard or adjust the reader's classifications.
Results of quality control classifications can also be used to provide feedback to readers to maintain and improve readers' performance.1 This approach eliminates the defects in other quality control approaches. This is true for those that are undertaken independently and externally to the study. It is also the case when a reader may consciously modify their behavior to appear more mainstream. Although using unknown calibration radiographs cannot eliminate all variation between readers, it should eliminate excesses.
Inter-reader comparisons
Passive quality control
In some settings, it may be beneficial to start preliminary classification activities where the same radiographs are classified independently by multiple readers and the findings reported back to the readers. This information may reveal a reader's differences from the mainstream. It will also provide an opportunity for further education and self-correction.
Active quality control
Information from preliminary procedures is employed in the final selection of readers by removing extreme readers at each end of the scale. Similar quality assurance exercises can also be done during any classification process involving multiple readers and radiographs. This will provide continuing feedback and maintenance of standards.
Active quality control provides a final check on reader consistency. However, such efforts provide only a form of relative quality assurance; the readers are compared only to each other and not to objective, external classifications. The only way to ensure true accuracy is to concurrently evaluate a "gold standard" such as calibration (quality assurance) radiographs with known classifications.
- Sheers G, Rossiter CE, Gilson JC, et al. UK naval dockyards asbestos study: radiological methods in the surveillance of workers exposed to asbestos. Br J Ind Med 1978; 35:195-203.