The Veteran’s Affairs (VA) data presented are from a national sample of health care visits to the VA Health System by eligible U. S. veterans. During any given year, roughly 70% of the outpatient population receives at least one serum creatinine test. While the demographics of VA Health System users are distinct from the general U.S. population, the VA data allow a snapshot of clinical practices across the nation.

National VA data were examined for veterans with at least one outpatient visit during the federal fiscal year. To estimate prevalence of CKD, outpatient serum creatinine laboratory results (averaged if a patient had more than one test during the fiscal year) were used to calculate an estimated glomerular filtration rate (eGFR) for each patient using the CKD-EPI equation, excluding dialysis and transplant patients. Estimated GFR (kidney function) was classified into five CKD categories (eGFR =90, eGFR 60-89, stage 3=eGFR 30-59, stage 4=eGFR 15 to 29, and stage 5 without dialysis=eGFR<15 ml/min/1.73 m² and “eGFR Unmeasured” for those patients without serum creatinine testing. Inpatient serum creatinine data were not used as they would be affected by the presence of acute illnesses. Due to the infrequency of testing, albuminuria was not included in the definition of CKD. Dialysis patients were defined by clinic stop-codes (602-611), outpatient procedure codes for dialysis (CPT4: 90921 and 90925), outpatient diagnosis codes (ICD-9-CM: 585.6, V56, V45.1 and E87.91) and inpatient and outpatient diagnosis codes (ICD-9-CM: 5856) to indicate dialysis. Kidney transplant patients were identified by inpatient and outpatient ICD-9-CM diagnosis code V420 and inpatient procedure and surgery codes (55.69).

To examine acute kidney injury (AKI) in the hospital setting within the VA, we determined an index hospitalization for each fiscal year. This was the patient's first hospitalization of the year that had a length of stay of 2 days or more with 2 or more inpatient serum creatinine test results. A baseline serum creatinine measurement was determined from outpatient serum creatinine test results at least 7 days prior to the index hospitalization. Patients with evidence of pre-admission end-stage renal disease or a baseline MDRD estimated GFR less than 15 were excluded. An episode of AKI during the index hospitalization was defined by an increase in serum creatinine from baseline of 0.3mg/dL that did not decrease within 48 hours.

All outpatient lab results between discharge and 6 months post discharge for patients alive 6 months after discharge were examined to see if a serum creatinine test was performed.

This material is the result of work supported with resources and the use of facilities at the Veterans Affairs Ann Arbor Healthcare System, Ann Arbor, Michigan.