IMPROVING UNDERSTANDING OF TEST RESULTS BY SUBSTITUTING (NOT ADDING) GOAL RANGES

Purpose: Presentations of laboratory test results typically include standard reference ranges. For some patients though, e.g. those with chronic conditions, achieving a result within the standard range may be inappropriate or even harmful. For example, it may be inadvisable for older patients with diabetes to aim for a Hemoglobin A1c within the standard range. We tested the impact of (a) adding a goal range to a visual display or (b) substituting the goal range for the standard range on people’s ability to identify the desirable direction for their next test.

Methods: Participants (N=3782) from a demographically diverse online panel were presented with a hypothetical scenario in which they received Hemoglobin A1c test results as part of Type 2 diabetes management. The scenario described a goal range of 6.5%-7.5% for people with Type 2 diabetes and the risks associated with an A1c that is too high or too low. Participants viewed their test result (A1c=6.2%) in visual displays that had one of three sets of reference ranges: (1) standard range (4.5%-5.7%) only, (2) goal range added to standard range or (3) goal range only. The primary outcome measure was whether patients recognized that their next test value should be moving higher towards the goal range. The secondary outcome measure was the extent to which the test value made the participant feel discouraged/encouraged (“Very discouraged" (1) - “Very encouraged" (6)). Individual difference measures included subjective numeracy, health literacy, and graphical literacy.

Results: A significantly higher percentage of participants in the goal range only condition (51%) correctly identified that their next test value should be higher compared to participants in the goal added to standard range (35%) and standard range only (23%) conditions (p<.001). Additionally, the goal range only condition produced greater encouragement (M=4.43, SD=1.32) than the goal added to standard range (M=4.29, SD=1.44) and standard range only (M=3.91, SD=1.45) conditions (p<.001).  Both analyses controlled for individual differences.

Conclusions: Providing a patient-appropriate goal range instead of (not in addition to) the standard range appears to improve people’s understanding of their test results compared to their target. Using such purpose-specific displays holds the potential to improve patient self-management of chronic conditions and avoid some harms of overtreatment by better calibrating patients’ expectations.