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

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

Passive Data Restriction Algorithm Step Muscular Dystrophy Fragile X Syndrome
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 134a
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 375a 141 50
  1. 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