Variation in Attitudes to Native Kidney Biopsy Practice in the United States.

Rationale & Objective: There is substantial variation in kidney biopsy practices within and between countries; however, the reasons for this are unclear due to limited research among large diverse populations. The aim of this study was to explore variations in attitude to the indications and contraindications for native kidney biopsy in the United States (US). Study Design: A case-vignette questionnaire was developed. A propensity-to-biopsy score (0-44) was generated from responses to indications and contraindications, with a higher score indicating an increased likelihood to recommend biopsy. Dissemination of the questionnaire occurred by email, social media, and the National Kidney Foundation. Setting & Participants: A total of 295 nephrologists/fellows from 43 states within the US participated. Exposure: All participants completed an identical questionnaire on kidney biopsy practice. Outcomes: Responses were collected on indications, contraindications, and attitudes to biopsy. Analytical Approach: Anonymized IP addresses were collected for comparison between US states. Data were also collected on the demographics of the individual and the type of institution in which the doctor was based. Results: In an adjusted multiple linear regression analysis, higher propensity-to-biopsy scores were demonstrated in US clinicians who were male, younger and more frequent performers of kidney biopsy (P = 0.05). There were significant differences between the 18 US states with 5 or more participants (P < 0.001) with the mean propensity-to-biopsy score ranging from 20.3 (Wisconsin) to 29.2 (New Jersey and Virginia). Increased biopsy propensity was also observed in US states with higher nephrologist density and lower statewide deprivation (P = 0.006). Limitations: The condensed clinical scenarios may not accurately replicate real-world cases, and clinicians opted in often using social media, so generalizability is limited. Conclusions: Attitudes to kidney biopsy practice in the US are highly variable, and clinician or institutional characteristics do not fully explain these discrepancies. Further research is required to understand the factors that influence clinical decision making.