Left-digit bias and deceased donor kidney utilization

Cognitive biases shown to impact medical decision-making include left-digit bias, the tendency to focus on a continuous variable's leftmost digit. We hypothesized that left-digit bias impacts deceased donor kidney utilization through heuristic processing of donor age and creatinine. We used US registry data to identify 87 019 kidneys recovered (2015-2019) and compared the proportion around thresholds for donor age (69 vs. 70 years) and creatinine (1.9 vs. 2.0 mg/dl), then compared the risk of kidney discard. Kidneys from donors aged 70 vs. 69 years were more frequently discarded (77% vs. 65%, p < .001), with higher risk of discard even after adjusting for KDRI (adjusted RR 1.11, 95% CI 1.02-1.21, p = .018). Similarly, kidneys from donors with final creatinine 2.0 vs. 1.9 mg/dl were more frequently discarded (37% vs. 29%, p < .001), with higher risk of discard after adjusting for KDRI (adjusted RR 1.19, 95% CI 1.07-1.33, p = .001). However, no significant left-digit effect was found when examining other donor age (39/40, 49/50, 59/60 years) or creatinine (0.9/1.0, 2.9/3.0 mg/dl) thresholds. The findings suggest a possible left-digit effect affecting kidney utilization at specific thresholds. Additional investigations of the impact of this and other heuristics on organ utilization are needed to identify potential areas for decision-making interventions aimed at reducing kidney discard.