Data Quality Considerations
Changes in the number of birth defect cases may reflect a change in birth defect reporting or identification, rather than a change in trend. In particular, during the late 1990s, certain reporting and diagnostic practices contributed to the number of cases identified. The changes by year are delineated below:
2010: A change in ICD-9 CM coding added unique codes for Gastroschisis and Omphalocele in October of 2009. This is the cause of the missing values in the reported frequencies for these conditions as listed under the diagnostic grouping "I03 Gastroschisis (756.73) and Omphalocele (756.72)."
1998: Increases in frequency of endocrine and metabolic disorders since 1998 are due to coordination of case reporting with the Newborn Metabolic Screening Program.
The increased number of cases diagnosed with hearing deficiency in evidence since 1997
is related directly to a rapid increase in screening of Michigan newborns for hearing loss
by birthing hospitals.
1996: A change in ICD-9 CM coding added unique codes for hypospadias and epispadias in October of 1996. This is the cause of the discontinuity in the reported frequencies for these conditions as listed under the diagnostic grouping "H04 Hypospadias and Epispadias (752.61, 752.62)."
Completeness and Over-reporting
The completeness of the data presented in these tables is affected by three
factors that relate to data accuracy and comparability. It is essential
that these factors be considered in using the information particularly when
comparing frequencies over time or between geographic areas. These factors
Over Reporting - The ongoing review of reports received has identified that in certain hospitals a report that a child has a reportable condition will be submitted, but the diagnosis is later ruled out and the original report is not corrected accordingly. This can cause an over count of the number of cases. This problem can be expected to vary by facility which, in turn, can lead to geographic variations in case frequency counts for those areas where such facilities are located.
Resident Interstate Information Exchange is Lacking - There is presently no exchange of data with neighboring states relative to children born with birth defects. Such exchange does occur with vital records and cancer information. The effect of this lack of a resident information exchange is that birth defects cases are unreported whenever a Michigan child is diagnosed with or treated for a birth defect in a facility that is not within Michigan. This problem will cause an undercount of the actual number of cases and can be expected to significantly affect the completeness of reports for counties whose residents commonly travel outside Michigan for their health care. It is due to the lack of interstate resident information exchange that rates are calculated only for resident children who are also born in Michigan.
Symbols Used In Tables
−−− Data not available.
− A dash indicates quantity zero.
* An asterisk indicates unstable rates that would be produced from small numbers. The figure does not meet standards of reliability or precision.