J. Paediatr. Child Health (2004) 40, 544–548 Validation study of the Victorian Birth Defects Register M Riley, 1 S Phyland 1 and J Halliday 1,2 1 Victorian Perinatal Data Collection Unit, Department of Human Services, and 2 Murdoch Children’s Research Institute, Royal Children’s Hospital, Melbourne, Victoria, Australia Objective: To determine whether there has been an improvement in ascertainment of birth defects cases (‘case validity’) by the Victorian Birth Defects Register (BDR) since an earlier study (conducted in 1993), to ascertain the accuracy of registered data (‘item validity’) and to investigate another possible source of notification. Methods: The medical records were reviewed of 500 children born after 1 January 1993 who were consecutively admitted after 1 January 1999 to two paediatric teaching hospitals in Victoria. In addition, records of 200 children referred to a clinical genetics service were reviewed for children born after 1 January 1993 and who were seen in two periods: 2 months after 1 January 2001 and 2 months after 1 January 2002. The records from the hospitals and clinical genetics service were reviewed separately to determine whether children recorded as having a birth defect had previously been notified to the BDR. Results: Twenty percent of the hospital records related to a child with a birth defect, as did 70% of the clinical genetics service records. Overall case validity for birth defect cases from the hospitals was 88%. There was 100% ascertainment for three of five categories. Sixty per cent of birth defects cases from the clinical genetics service had been notified to the BDR. When all diagnoses in matched cases were considered, item validity was 54%, however, if only primary diagnoses were included then 92% of cases had the same diagnosis. Conclusions: Overall case validity from the two paediatric teaching hospitals has significantly improved since our previous study. The addition of an extra data source from a clinical genetics service would identify new cases, particularly genetic disorders and developmental delay, as well as adding new diagnoses to existing ones.This study has highlighted the need to improve item validity, perhaps through routine education for all coders and notifiers on the inclusion and exclusion of specific associated conditions when notifying major birth defects. Key words: birth defects; congenital malformations; quality control; validation. The Victorian Birth Defects Register (BDR) was established in January 1984 within the Victorian Perinatal Data Collection Unit (VPDCU) of the Victorian Department of Human Ser- vices. The BDR receives notifications on birth defects amongst livebirths, stillbirths and terminations of pregnancy for cases identified since 1 January 1982, irrespective of the age at diagnosis up to 15 years of age. 1 Notifiable birth defects are defined as an abnormality in body structure, function or chemistry, present at birth, but not necessarily noticed at birth. 2 Notification of birth defects to the BDR is voluntary and depends upon many different sources. Therefore, the number of notifications exceeds the number of cases due to multiple reporting of cases from the various notifiers. Sources of notifi- cation include: VPDCU – Perinatal Morbidity Statistics Forms; perinatal death certificates; autopsy reports; cytogenetics reports; maternal and child health nurses; hospital listings; other health professionals and other sources, including parents. The number of notifications per case is approximately 1.4. 2 To enable a population-based register that relies on volun- tary notification to be utilized effectively for research and planning, it is important to know how accurate and complete the data are. Different attempts at validating information in other registries are reported in the literature. 3–7 A common approach 3–5 appears to be a comparison of overall prevalence figures of selected major defects between birth registries. Other methods include comparison with hospital morbidity statistics systems, either statewide 3 or hospital based 7 or comparison with registers of special interest groups, for example, Cleft Lip and Palate Register. 3 The ‘validity’ of the register is dependent upon the validation tool chosen. Stone 8 refers to two types of validity: 1 the ascertainment of infants believed to be malformed (‘case validity’) and, 2 the accuracy of registered data (‘item validity’). The BDR has undertaken two previous published studies 7,9 on case validity, and informally reviewed item validity in student projects. 10 It is the aim of this study: (i) To determine if case validity has improved since the previous study (1993), (ii) To assess item validity, (iii) To assess the impact on case validity of adding a new data source. METHODS A total of 700 records were reviewed. Two paediatric teaching hospitals and a clinical genetics service participated in the study. The procedure was the same for the two notification sources, involving review of records related to: ● 250 consecutive hospital admissions from 1 January 1999, of children born since 1 January 1993, from each hospital, i.e. 500 hospital medical records. ● 200 consecutive referrals of children to the clinical genetics service: 100 born since 1 January, 1993, and referred in 2001, and 100 born since 1 January, 1994, and referred in 2002. Correspondence: Merilyn Riley, Perinatal Data Collection Unit, GPO Box 4003, Melbourne, Vic. 3001, Australia. Fax: +61 3 9616 2700; email: merilyn.riley@dhs.vic.gov.au Accepted for publication 11 March 2004.