A Prospective Longitudinal Assessment of Medical Records for Diagnostic Substitution among Subjects Diagnosed with a Pervasive Developmental Disorder in the United States

BACKGROUND: Previously, investigators suggested that diagnostic substitution from other diagnoses, e.g., mental retardation (MR) and/or cerebral palsy (CP) to pervasive developmental disorder (PDD) is a driving factor behind increases in autism. This study evaluated potential diagnostic substitution among subjects diagnosed with PDD vs. MR or CP by examining birth characteristic overlap. METHODS: SAS(®) and StatsDirect software examined medical records for subjects within the Vaccine Safety Datalink database who were Health Maintenance Organization-enrolled from birth until diagnosed with an International Classification of Disease, 9th revision (ICD-9) outcome of PDD (299.xx, n = 84), CP (343.xx, n = 300), or MR (317.xx, 318.xx, or 319.xx, n = 51). RESULTS: Subjects with PDD had significantly (p < 0.01) increased: male/female ratio (PDD = 5.5 vs. CP = 1.5 or MR = 1.3), mean age of initial diagnosis in years (PDD = 3.13 vs. CP = 1.09 or MR = 1.62), mean gestational age in weeks at birth (PDD = 38.73 vs. CP = 36.20 or MR = 34.84), mean birth weight in grams (PDD = 3,368 vs. CP = 2,767 or MR = 2,406), and mean Appearance-Pulse-Grimace-Activity-Respiration scores at 1 min (PDD = 7.82 vs. CP = 6.37 or MR = 6.76) and 5 min (PDD = 8.77 vs. CP = 7.92 or MR = 8.04), as compared to subjects diagnosed with CP or MR. CONCLUSION: This study suggests diagnostic substitution cannot fully explain increased PDD prevalence during the 1990s within the United States.