Technical Note: 30-Day Mental Illness Readmission Rate

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Technical Note

30-Day Mental Illness Readmission Rate

Unit of Analysis

The unit of analysis is an episode of care. An episode of care refers to all contiguous inpatient hospitalizations in general hospitals1 and day surgery visits regardless of diagnoses. To construct an episode of care a transfer is assumed to have occurred if the following condition is met:

  • Admission to a general hospital/day surgery facility occurs on the same day as discharge from another general hospital.

Denominator (Index Episode)

Number of episodes of care for selected mental illness. These episodes are identified as follows:

Inclusion Criteria

  1. A selected mental illness is coded as most responsible diagnosis (MRDx)
    Diagnosis codes for selected mental illness:
    1. Substance-related disorders—ICD-10-CA: F55, F10 to F19; DSM-IV: 291.x (0, 1, 2, 3, 5, 81, 89, 9), 292.0, 292.11, 292.12, 292.81, 292.82, 292.83, 292.84, 292.89, 292.9, 303.xx (00, 90), 304.xx (00, 10, 20, 30, 40, 50, 60, 80, 90), 305.xx (00, 10 to 90 excluding 80); or
    2. Schizophrenia, delusional and non-organic psychotic disorders—ICD-10-CA: F20 (excluding F20.4), F22, F23, F24, F25, F28, F29, F53.1; DSM-IV: 295.xx (10, 20, 30, 40, 60, 70, 90), 297.1, 297.3, 298.8, 298.9; or
    3. Mood/affective disorders—ICD-10-CA: F30, F31, F32, F33, F34, F38, F39, F53.0; DSM-IV: 296.0x, 296.2x, 296.3x, 296.4x, 296.5x, 296.6x, 296.7, 296.80, 296.89, 296.90, 300.4, 301.13; or
    4. Anxiety disorders—ICD-10-CA: F40, F41, F42, F43, F48.8, F48.9, F93.8; DSM-IV: 300.xx (00, 01, 02, 21, 22, 23, 29), 300.3, 308.3, 309.x (0, 3, 4, 9), 309.24, 309.28, 309.81; or
    5. Selected disorders of adult personality and behaviour—ICD-10-CA: F60, F61, F62, F68, F69, F21; DSM-IV: 301.0, 300.16, 300.19, 301.20, 301.22, 301.4, 301.50, 301.6, 301.7, 301.81, 301.82, 301.83, 301.9.
  2. Discharges between April 1 and March 1 of the following year (period of case selection ends on March 1 to allow for 30 days of follow-up)
  3. Age at admission is 15 years or older
  4. Sex recorded as male or female
  5. Admission to a general hospital
  6. Canadian resident

Exclusion Criteria

  1. Records with an invalid health card number
  2. Records with an invalid date of birth
  3. Records with an invalid admission date
  4. Records with an invalid discharge date
  5. Discharged as a death

Numerator

Inclusion Criteria

An episode of care is considered a readmission if the two following conditions are met:

  1. It has occurred within 30 days of discharge of an index episode
  2. A diagnosis of mental illness was recorded (see denominator for criteria to select diagnosis)

1 Excludes free-standing psychiatric facilities.