Abstract
Introduction: The agreement of clinical coding between rural and urban hospitals in Aotearoa New Zealand (NZ) is unknown, and data from comparable international health systems is scarce, dated or inconclusive. There is a reliance upon administrative datasets that store clinically coded information to complete numerous rural-urban health analyses, which inform health policy and resource allocation decisions. Anecdotally, clinical coding in NZ rural hospitals is often performed by clinicians or reception staff without formal coding training; in urban NZ hospitals this would usually be completed by formally trained clinical coders. This study aimed to determine whether discrepancies existed between the primary diagnosis codes assigned in the National Minimum Dataset (hospital events) (NMDS) of hospital discharges by NZ's publicly funded hospitals, for patients who underwent an interhospital transfer from a rural to an urban hospital.
Methods: This was a retrospective observational study using the NMDS. NZ's publicly funded hospitals were classified into three categories: rural hospitals, hospitals in small urban centres and hospitals in large urban centres. Interhospital transfers were identified by bundling events in the NMDS into healthcare encounters. The primary diagnosis codes assigned at discharge from the rural hospital were compared against the codes assigned at discharge from the urban hospital, and corresponding diagnosis groups based on the WHO chapter definitions were assigned to each code. The number and percentage, with 95% confidence intervals (CIs), of encounters where there was discordance between primary diagnosis codes from the rural and urban hospitals were calculated.
Results: The study included 31,691 patients, from 54 publicly funded hospitals, who underwent an interhospital transfer from an NZ rural to an urban hospital between 1 January 2015 and 31 December 2019. There were discrepancies in 64.1% (95%CI 63.5-64.6%) of the primary diagnosis codes assigned between the rural and urban hospitals, and in 32.1% (95%CI 31.6-32.6%) of broader diagnosis groups. In both cases, higher discrepancies existed for transfers to hospitals in small urban centres compared to hospitals in large urban centres. The most frequently assigned diagnosis group at discharge from rural hospitals was the non-specific group 'other', constituting 24.4% of all diagnosis groups assigned by a rural hospital. For 4.8% of all healthcare encounters, a specific diagnosis group assigned on discharge from the rural hospital was subsequently changed to 'other' at the urban transfer hospital. This reassignment to 'other' following interhospital transfer occurred within every diagnosis group assigned at a rural hospital.
Conclusion: Two-thirds of primary diagnosis codes and one-third of diagnosis groups were discordant after transfer from rural to urban hospitals in NZ. Further investigation is needed into why these discrepancies are occurring.