Validation of Diagnostic Coding for Diabetes Mellitus in Hospitalized Patients

Some studies have shown that there is an undercoding of diabetes mellitus among hospitalized patients, which can have adverse clinical and financial implications for health systems. We aimed to validate the discharge diagnostic coding of diabetes mellitus in hospitalized patients using clinical and laboratory-based diagnostic indicators as the reference.

This was a retrospective cohort study of 83 690 discharges of 48 615 unique adult patients who were hospitalized in an academic medical center over 4.5 years and had at least 4 blood glucose measurements during admission. A missing diabetes code (MDC) was defined using 2 criteria. MDC₁ was defined as the presence of any of the following: blood glucose ≥200 (x2), A1C ≥6.5%, home antihyperglycemic medication, or preadmission code for diabetes, whereas MDC₂ was defined as preadmission diabetes or at least 2 other criteria in MDC₁. Multivariable logistic regression was used to identify factors associated with MDC compared to the present diabetes code.

MDC₁ and MDC₂ were present in 12 186 (14.6%) and 3542 (4.7%) discharges, respectively. Factors associated with both MDC₁ and MDC₂ were medium-dose steroid use [adjusted odds ratio (aOR) 2.11, 2.01], high-dose steroid use (aOR 4.70, 2.50), intermediate medical care service (aOR 1.65, 1.55), infection (aOR 1.21, 1.34), and hepatic disease (aOR 1.93, 1.92).

In this retrospective study, MDC ranged from 5% to 15% and was associated with various clinical factors. Further prospective studies are needed to validate these findings, explore the mechanisms behind these associations, and understand the clinical and financial implications.