False positive reporting of Hirschsprung's disease in Alaska: An evaluation of Hirschsprung's disease surveillance, birth years 1996-2007

The Accuracy of Hospital Discharge Diagnosis Codes for Major Birth Defects: Evaluation of a Statewide Registry With Passive Case Ascertainment

CONTEXT

Birth defects prevention, research, education, and support activities can be improved through surveillance systems that collect high-quality data.

OBJECTIVE

To estimate the overall and defect-specific accuracy of Florida Birth Defects Registry (FBDR) data, describe reasons for false-positive diagnoses, and evaluate the impact of statewide case confirmation on frequencies and prevalence estimates.

DESIGN

Retrospective cohort evaluation study.

PARTICIPANTS

A total of 8479 infants born to Florida resident mothers between January 1, 2007, and December 31, 2011, and diagnosed with 1 of 13 major birth defects in the first year of life.

MAIN OUTCOME MEASURES

Positive predictive value: calculated overall (proportion of FBDR-identified cases confirmed by medical record review, regardless of which of the 13 defects were confirmed) and defect-specific (proportion of FBDR-identified cases confirmed by medical record review with the same defect) indices.

RESULTS

The FBDR's overall positive predictive value was 93.3% (95% confidence interval, 92.7-93.8); however, there was variation in accuracy across defects, with positive predictive values ranging from 96.0% for gastroschisis to 54.4% for reduction deformities of the lower limb. Analyses suggested that International Classification of Diseases, Ninth Edition, Clinical Modification, codes, upon which FBDR diagnoses are based, capture the general occurrence of a defect well but often fail to identify the specific defect with high accuracy. Most infants with false-positive diagnoses had some type of birth defect that was incorrectly documented or coded. If prevalence rates reported by the FBDR for these 13 defects were adjusted to incorporate statewide case confirmation, there would be an overall 6.2% rate reduction from 82.6 to 77.5 per 10 000 live births.

CONCLUSIONS

A statewide birth defects surveillance system, relying on linkage of administrative databases, is capable of achieving high accuracy (>93%) for identifying infants with any one of the 13 major defects included in this study. However, the level of accuracy and the ability to minimize false-positive diagnoses vary depending on the defect.

Testing the Feasibility of a Passive and Active Case Ascertainment System for Multiple Rare Conditions Simultaneously: The Experience in Three US States

Background

Owing to their low prevalence, single rare conditions are difficult to monitor through current state passive and active case ascertainment systems. However, such monitoring is important because, as a group, rare conditions have great impact on the health of affected individuals and the well-being of their caregivers. A viable approach could be to conduct passive and active case ascertainment of several rare conditions simultaneously. This is a report about the feasibility of such an approach.

Objective

To test the feasibility of a case ascertainment system with passive and active components aimed at monitoring 3 rare conditions simultaneously in 3 states of the United States (Colorado, Kansas, and South Carolina). The 3 conditions are spina bifida, muscular dystrophy, and fragile X syndrome.

Methods

Teams from each state evaluated the possibility of using current or modified versions of their local passive and active case ascertainment systems and datasets to monitor the 3 conditions. Together, these teams established the case definitions and selected the variables and the abstraction tools for the active case ascertainment approach. After testing the ability of their local passive and active case ascertainment system to capture all 3 conditions, the next steps were to report the number of cases detected actively and passively for each condition, to list the local barriers against the combined passive and active case ascertainment system, and to describe the experiences in trying to overcome these barriers.

Results

During the test period, the team from South Carolina was able to collect data on all 3 conditions simultaneously for all ages. The Colorado team was also able to collect data on all 3 conditions but, because of age restrictions in its passive and active case ascertainment system, it was able to report few cases of fragile X syndrome. The team from Kansas was able to collect data only on spina bifida. For all states, the implementation of an active component of the ascertainment system was problematic. The passive component appears viable with minor modifications.

Conclusions

Despite evident barriers, the joint passive and active case ascertainment of rare disorders using modified existing surveillance systems and datasets seems feasible, especially for systems that rely on passive case ascertainment.