MA03.11 Cognitive Bias in Lung Cancer Surgery: The Left Digit Effect

Leading digit bias in hemoglobin thresholds for red cell transfusion

BACKGROUND

Leading digit bias is a heuristic whereby humans overemphasize the left-most digit when evaluating numbers (e.g., 9.99 vs. 10.00). The bias might affect the interpretation of hemoglobin results and influence red cell transfusion in hospitalized patients.

STUDY DESIGN AND METHODS

Adults who received a red cell transfusion while registered at the University Health Network (Toronto, Canada) between January 1, 2016 and January 1, 2022 (n = 6 years) were included. The primary analysis excluded apheresis, red cell disorders, radiology suites, and operating rooms. The primary comparison was a regression discontinuity analysis of transfusion occurrence above and below the hemoglobin threshold of 79 g/L (local units). Additional analyses tested other leading digit and control thresholds (71, 81, and 91 g/L). Secondary analyses explored temporal covariates and clinical subgroups.

RESULTS

A total of 211,872 red cell transfusions were identified over the study period (median pre-transfusion hemoglobin 76 g/L; interquartile range = 69-92 g/L), with 107,790 inpatient transfusions in the primary analysis. The 79 g/L threshold showed 815 fewer red cell units above the threshold (95% confidence interval [CI]: -1215 to -415). The 69 g/L threshold showed 2813 fewer transfused units (95% CI: -4407 to -1220), and 89 g/L showed 40 fewer units (95% CI: -408 to 328). The effect was accentuated during daytime, weekday, and May-June months, persisted in analyses including all transfusions, and was absent at control thresholds.

CONCLUSION

Leading digit bias might have a modest influence on the decision to transfuse red cells. The findings may inform practice guidelines and quasi-experimental study design in transfusion research.

Left-digit bias in surgical decision-making for lumbar spinal stenosis

BACKGROUND CONTEXT

Left-digit bias is a behavioral heuristic or cognitive "shortcut" in which the leftmost digit of a number, such as patient age, disproportionately influences surgical decisions.

PURPOSE

To determine if left-digit bias in patient age influences the decision to perform arthrodesis with instrumentation vs decompression in lumbar spinal stenosis (LSS).

DESIGN

Retrospective cohort.

PATIENT SAMPLE

Patients with an ICD-10 diagnosis of lumbar stenosis or spondylolisthesis identified in the 2017-2021 National Surgical Quality Improvement Program (NSQIP) database.

OUTCOME MEASURES

The primary outcome was the percent of patients who underwent arthrodesis with instrumentation (AwI). Matched age group comparisons without left-digit differences (ie, 76/77 vs 78/79, 80/81 vs 82/83, etc.) were performed to isolate the effect of the heuristic. Secondary outcomes including peri-operative events and complications were also compared within AwI and decompression cohorts.

METHODS

Using CPT codes, procedures were classified as either AwI or decompression. Patients were grouped into 6 cohorts based on 2-year age windows (74/75, 76/77, 78/79, 80/81, 82/83, 84/85). The cohorts were propensity matched with neighboring age groups based on the presence of spondylolisthesis, demographics, and comorbidities. The primary comparison was between those aged 78/79 vs 80/81.

RESULTS

After matching, the primary cohort consisted of two groups of 1,550 patients (aged 78/79 and 80/81). Patients aged 80/81 were less likely to undergo AwI than patients aged 78/79 (23.5% vs 27.2%, p=.021). AwI procedures occurred at similar rates between age groups with the same left digit. Within the decompression and AwI cohorts, there were no differences in secondary outcomes between patients aged 78/79 and 80/81.

CONCLUSIONS

LSS patients aged 80/81 are less likely to undergo AwI than patients aged 78/79, regardless of comorbidities. This was not seen when comparing patients with similar left digits in age. Until objective measures of physiologic capacity are established, left-digit bias may influence clinical decisions.

An assessment of left-digit bias in the treatment of older patients with potentially curable rectal cancer

BACKGROUND

Patient age is associated with poorer rectal cancer treatment compliance. However, it is unknown whether left-digit bias (disproportionate influence of leftmost age digit) influences this association.

METHODS

The patients diagnosed with stage I-III rectal cancer between 2006 to 2017 in the National Cancer Database were identified. The association between age and receipt of guideline-adherent care was assessed using mixed-effects multivariable analyses.

RESULTS

Among 97,960 patients, 46.2% received guideline-adherent overall treatment and 73.3% underwent guideline-adherent surgical resection. Of those who underwent guideline-adherent surgery, 86.4% received guideline-adherent radiotherapy and 56.6% received guideline-adherent chemotherapy. After risk-adjustment, each decade increase in age was associated with 36% decreased odds of guideline-adherent therapy (odds ratio = 0.64, 95% confidence interval = 0.63-0.65). Patients aged 58 to 59 (odds ratio = 1.15, 95% confidence interval = 1.02-1.27) and 78 to 79 (odds ratio = 1.28, 95% confidence interval = 1.08-1.51) had higher odds of guideline-adherent overall treatment compared with patients aged 60 and 80, respectively. However, there were no significant differences in the receipt of guideline-adherent treatment between patients aged 60 vs 61-62 and 80 vs 81-82.

CONCLUSION

Older patients with rectal cancer are less likely to receive guideline-adherent care, and a left-digit bias is present. Geriatric assessment-guided treatment decisions could help mitigate this bias.