The recent study by Ruutiainen and colleagues offers an opportunity to reflect on an epistemological concept known as Wittgenstein’s ruler, which alludes to the difference between subjective and objective measurements.
Although this study is by no means unique in the use of purportedly objective indices that bear on subjectivity, the circumstances in which the metrics “major change” and “minor change” have been used are likely to be familiar to radiologists in resident training programs and thus this study presents an opportunity to discuss Wittgenstein’s ruler.
Objective versus the subjective
Ludwig Wittgenstein, a German philosopher from the 20th century, made the distinction between an objective ruler and a subjective ruler . An objective ruler, if set out to measure the length of the table, tells us about the length of the table; both the scale and the measured have a commonality—notably a unit of length. When measuring a table, so to speak, by a subjective ruler, we find out as much about the ruler as we do about what the ruler purports to measure. In other words, the table is measuring the ruler just as the ruler is measuring the table.
Consider book reviews. Reviews tell us just as much about the reviewers and their world view in general and views of the subject matter in particular, as they do about the book. Indeed, on reading the review one can guess the nature of the publication and the ideological inclination of the publication. The reader may wish to experiment this by reading the reviews of Salman Rushdie’s Joseph Anton in the (right-leaning) Wall Street Journal and (left-leaning) Guardian .
Subjectivity is inevitable and, in some situations, unavoidable. Subjectivity should not be maligned; rather explicitly acknowledged as being part of the measuring instrument.
Residual subjectivity
In the aforementioned study, the authors have used a metric to determine the severity of the discrepancy between final attending read and the preliminary resident interpretation of an imaging study. A “major change” denotes a significant disagreement between the attending and the resident. The term “significant” is not simply a disagreement of grammatical construction and semantic emphasis in the report; recognizing that such differences can be significant or, at the very least, have a significant untoward effect on the attending. The significance of the disagreement lies in the potential impact on patient care that may have arisen if the preliminary report was taken at face value or to its logical conclusion. This is a disagreement about the substance of the interpretation not style of the report; considerable diligence and neutrality may be required separating the two on occasion.
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Significant disagreements versus disagreements about significance
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The broad potential of “potential”
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What does the judgment tell us about the adjudicator?
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The attending radiologist as the arbiter of truth
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Combatting the variation—a sisyphean task?
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Embracing the gray zone
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Conclusion
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References
1. Ruutiainen A.T., Durand D.J., Scanlon M.H., et. al.: Increased error rates in preliminary reports issued by radiology residents working more than 10 consecutive hours overnight. Acad Radiol 2013; 20: pp. 305-311.
2. Wittgenstein L. Tractatus logico-philosophicus. 2.15. Project Gutenberg. 2010.
3. Life in the Fatwa’s shadow. Book review. Wall Street Journal September 17, 2012.
4. Joseph Anton by Salman Rushdie. Book review. Guardian September 18, 2012.
5. The National Lung Screening Trial Research Team: Reduced lung-cancer mortality with low-dose computed tomographic screening. N Engl J Med 2011; 365: pp. 395-409.
6. Welsh A.H., Townsend Peterson A., Altman S.A.: The fallacy of averages. Am Naturalist 1988; 132: pp. 277-288.