TEST RESULTS IN LINE GRAPHS INSTEAD OF TABLES: LESS CONFUSION WITHOUT DISTORTION
Method: We conducted an online survey experiment in which participants imagined receiving hemoglobin A1c test results in-between clinical visits for management of Type 2 diabetes. Adults (N=1,785) viewed their mock results in one of three formats: (1) standard table that included the test result and a standard range, (2) table with an indicator for whether a result was high or low, or (3) a horizontal line graph that visually showed the test result and standard range. We also varied whether A1c was within the standard range (5.4%), or one of three higher levels (6.4%, 7.1%, or 8.4%). Our primary outcome measure was participants’ ratings of how good or bad they thought the test value was (or whether they marked “don’t know”). Secondary measures included 4 questions related to graph preferences. We also assessed participant numeracy using both subjective and objective scales as well as graphical literacy.
Result: Controlling for numeracy and graphical literacy, significantly more respondents marked “don’t know” for how good or bad the test result was when they viewed the table without markers (OR=2.42, p<.001) or table with markers (OR=2.23, p<.001) than when they viewed the line graph. Subjective numeracy strongly predicted “don’t know” responses (p<.001), but neither objective numeracy (p=.09) nor graphical literacy (p=.14) were significant predictors. Mean risk perceptions varied by A1c level (p<.001) and were significantly predicted by subjective numeracy, objective numeracy, and graphical literacy (all p’s<.001), but were not significantly different across formats. The 4 graph perception questions were highly correlated (Cronbach’s alpha=0.89), and respondents significantly preferred the line graphs compared to either table format (p=.003).
Conclusion: Presenting laboratory test results in the commonly-used table formats, even those with high/low markers, can confuse patients. Visual line graph displays improve patient understanding and satisfaction and could be easily implemented into patient electronic health record portals.