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Table 1 Construction of study cohort

From: Mental illness and intensification of diabetes medications: an observational cohort study

Sample size n Criterion MHC Yes MHC No
   n(%) n(%)
440,953 Diabetic veteran VA outpatient treated with oral antiglycemic (during the 6 months prior to the OI), who was alive at start of OI and for whom MHC status can be determined 80,798 360,155
    
427,335 VA outpatient use in OI* 80,745 346,590
   100% 96%
    
426,605 Non-institutionalized in OI 80,344 346,261
   100% 100%
    
426,454 No data problems 80,323 346,131
   100% 100%
    
366,066 No conditions likely to alter goals of care§ 67,099 298,967
   84% 86%
    
315,063 Patient’s home facility submitted usable HbA1c lab data to central data repository 57,309 257,754
   85% 86%
    
269,692 Had at least one HbA1c test completed during the OI 51,582 218,110
   90% 85%
    
  Poor glycemic control: Had at least one HbA1c ≥8 during OI eligible to serve as an index HbA1c: 20,803 71,572
36% 28%
  (1) no antiglycemic intensification in the 3 months prior to the HbA1c test, AND 18,802 65,458
90% 91%
  (2) no hospitalization in the 3 months prior to the HbA1c test, AND 18,197 64,670
97% 99%
  (3) not occurring on a hospital admission day, AND 18,180 64,629
100% 100%
58,364 (4) no insulin prescribed in the 6 months prior to the HbA1c test 11,581 46,783
64% 72%
    
52,526 Final analytic cohort: Testing data set (90% random sample) 10,422 42,104
   90% 90%
  1. Legend: This table shows sample size at each step of cohort construction, overall and for those with/ without Mental Health Conditions; % reported in a row refers to % of prior row remaining after applying the inclusion criterion listed in current row.
  2. *Utilization refers to VA face-to-face outpatient care of any type; telephone, laboratory or radiology encounters did not qualify as face-to-face. Note that percentages in each row use the number in the prior row as denominator.
  3. Did not spend more than half the year in a VA inpatient or long-term care setting.
  4. Data quality issues such that unique identifier (scrambled social security number), date of birth or vital status was indeterminate.
  5. §End-stage renal disease, end-stage liver disease, cancer, stroke or dementia diagnosis occurring in the two years prior to the observation interval.
  6. Abbreviations: OI, Observation Interval (April 1, 2003 through March 31, 2004); MHC, Mental Health Condition; HbA1c, Hemoglobin A1c; VA, Veterans Health Administration.