Capture-recapture methodology to study rare conditions using surveillance data for fragile X syndrome and muscular dystrophy

Table 3 Number of cases identified in active and passive surveillance systems at each step of the passive data restriction algorithm

Passive Data Restriction Algorithm Step	Muscular Dystrophy		Fragile X Syndrome
Passive Data Restriction Algorithm Step	Cases Identified - Active	Cases Identified - Passive	Cases Identified - Active	Cases Identified - Passive
1. Cases with at least one ICD-9-CM code	384	3,305	141	795
2. Cases with at least one ICD-9-CM code given in a facility in target counties	384	1,428	141	231
3. Cases with at least one in-patient ICD-9-CM code or at least two outpatient ICD-9-CM codes given in a facility in target counties	384	990	141	134^a
4. Cases with at least one in-patient ICD-9-CM code or at least two outpatient ICD-9-CM codes given in a facility in target counties where at least one of the diagnoses was made by a neurologist, geneticist, or developmental pediatrician	384	375^a	141	50

^aIndicates the step at which the number of cases identified through the passive system is an underestimate of the cases identified through the active system

ISSN: 1750-1172