SAFTINet Asthma Cohort Definition Slideset. 31 Jan 2011

1. M A R I O N S I L L S
J A N U A R Y 3 1 , 2 0 1 1
Asthma Cohort Definitions

2. What Research Design Says
 “a longitudinal cohort…with persistent asthma will be
selected”
 “We will define asthma as a physician-documented
diagnosis of asthma using ICD-9-CM diagnosis codes
specified in the AHRQ Pediatric and Adult Asthma
Quality Indicator metric”
 “We will define persistent asthma as being present in an
individual who has one or more prescriptions for an
asthma therapy in the past 12 months or for those
without these medications prescribed, two or more
asthma related visits (first code) to the emergency room
or any hospitalization for asthma.”

3. AHRQ Quality Indicators: Asthma
 Adult: age 18 years and older
 Child: age 2-17 years
 ICD-9-CM principal diagnosis code of asthma
 Exclude cases:
 MDC 14 (pregnancy, childbirth, and puerperium)
 Transfer from other institution
 With diagnosis code for cystic fibrosis and anomalies of the
respiratory system
 (Indicator: asthma admission rate in region)

4. What Research Design Says
 Diagnosis of asthma using diagnosis codes* specified
in the AHRQ Asthma Quality Indicator metric
AND
 >1 prescriptions for asthma therapy in past 12 months
OR
 No meds and >2 ED or inpatient visits for asthma
 *inpatient diagnostic code in AHRQ measure—can it
apply to an outpatient setting?

5. What Research Design Says
 Inpatient diagnostic code in AHRQ measure—can it
apply to an outpatient setting?
 A single 493 code in two years is probably more
representative of a wheezing symptom for another
condition, not asthma (specificity ~60%)
 Performs even worse in children less than 5 years (viral
wheezing) and in older adult smokers (COPD)

6. Sources for Outpatient Asthma Cohort Definition
 Guidelines relevant to outpatient setting
 Studies using EHR/claims data

7. Sources for Outpatient Asthma Cohort Definition
 Guidelines relevant to outpatient setting
 Studies using EHR/claims data

8. Sources for Outpatient Asthma Cohort Definition
 Guidelines relevant to outpatient setting
 HEDIS
 Studies using EHR/claims data

9.  In past 12* months:
 > 4 asthma medication dispensing events
OR
 > 2 asthma medication dispensing events + 4 asthma-related
outpatient visits
OR
 > 1 asthma-related hospitalization
OR
 > 1 asthma-related ED visits
 *better = 24
HEDIS Definition: “Persistent Asthma”

10. HEDIS Outcome Measures
 Ratio of controller to total asthma medications > 0.5
 Prescription of > 1 controller medication
 Minimize circularity with cohort definition measures
 Process measures of healthcare quality, but are they
measures of control?

11. NIH Guideline Definition of Control
 Two components:
 severity
 the intrinsic intensity of the disease,
 used only for patient on no meds currently
 research design: cohort = persistent asthma: how to define?
 control (the degree to which the asthma symptoms are
minimized by meds)

12. Sources for Outpatient Asthma Cohort Definition
 Guidelines relevant to outpatient setting
 Studies using EHR/claims data

13. Studies Using EHR/Claims Data
 >2 visit-associated codes of 493 over 18 months
(visits must be separated by at least 4 weeks)
 Additive criterion: > 2 Rx for controller medications over 12
months
 Problem list diagnosis of asthma (providers
sometimes use “wheezing” as diagnosis to avoid pre-
existing condition issue)
 PFTs with reversibility to near or above normal—
increase of 12% and 200 cc if pre-bronchodilator
FEV1 is <80% (to distinguish from COPD in smokers
>45 years)

14. Exclusions to Consider
 Smokers over 65 (most have COPD)
 COPD (later consider studying combined COPD and
asthma)
 Alpha-1 antitrypsin
 Cystic fibrosis
 Any chronic lung disease (e.g., arising from
prematurity)
 Severe neurological condition (e.g., CP)

15. Outcomes in Prior Studies
 Utilization indicative of poor control
 ED, inpatient, ICU visits: rare
 Outpatient prescriptions for systemic steroids
 Clustered outpatient visits for asthma (3 OP/ED visits in 14
days)
 Combination of the above
 PFTs/FEV1: very rare
 Patient reported outcomes