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Validation of ICD-9-CM and ICD-10-CM Diagnosis Codes for Identifying Preterm Birth and Low Birthweight Infants in
Rachel E Rutkowski1, Jean Paul Tanner1, Scott D Grosse2
1Birth Defects Surveillance Program, Chiles Center, College of Public Health, University of South Florida, Tampa, FL.
Insights
Hospital discharge data accurately identify most preterm birth (PTB) and low birthweight (LBW) infants. However, coding accuracy decreases for cases near classification thresholds, requiring researchers to adjust for potential misclassification.
Area of Science:
- Medical Informatics
- Public Health
- Neonatal Research
Background:
- Accurate identification of preterm birth (PTB) and low birthweight (LBW) is crucial for neonatal health research.
- Diagnosis codes in hospital discharge data are often used for these classifications, but their accuracy needs validation.
Purpose of the Study:
- To evaluate the sensitivity and positive predictive value (PPV) of ICD-9-CM and ICD-10-CM diagnosis codes for identifying PTB and LBW infants.
- To compare coding accuracy before and after the transition to ICD-10-CM.
Main Methods:
- A population-based validation study using linked Florida birth certificate and infant hospital discharge records (2008-2018).
- Birth certificate data served as the reference standard for PTB (<37 weeks) and LBW (<2,500 g).
- Sensitivity and PPV were calculated for PTB and LBW codes across various strata.
Main Results:
- High PPV (>92% for PTB, >97% for LBW) was observed in both coding eras.
- Sensitivity improved post-ICD-10-CM transition (PTB: 77.0% to 84.4%; LBW: 73.3% to 76.9%).
- Lower sensitivity was found for cases near classification thresholds; accuracy was higher in urban teaching hospitals.
Conclusions:
- Infant hospital discharge data are reliable for identifying extreme PTB and LBW cases.
- Under-ascertainment of cases near classification thresholds necessitates adjustments in research, such as quantitative bias analysis.
Objective:
To estimate the sensitivity and positive predictive value (PPV) of ICD-9-CM and ICD-10-CM diagnosis codes for identifying preterm birth (PTB) and low birthweight (LBW) infants in birth hospital discharge data, using birth certificate records as the reference standard.
Methods:
We conducted a population-based validation study of Florida live births from 2008-2018 using linked birth certificate and infant hospital discharge records. Birth certificate obstetric estimates and recorded birthweights served as the reference standards. We calculated sensitivity and PPV for International Classification of Diseases, Ninth Edition, Clinical Modification (ICD-9-CM) and Tenth Edition (ICD-10-CM) diagnosis codes for PTB (<37 weeks) and LBW (<2,500 g) overall, by gestational-age and birthweight strata, and across maternal and hospital characteristics.
Results:
Among 2,166,535 infants, 10.3% were preterm and 8.7% LBW. PPV exceeded 92% for PTB and 97% for LBW in both coding eras. Sensitivity improved from 77.0% to 84.4% for PTB and from 73.3% to 76.9% for LBW after the ICD-10-CM transition. Sensitivity for diagnosis codes was notably lower nearest the binary classification thresholds for PTB (37 weeks) and LBW (2500 grams). Coding accuracy was higher in urban teaching hospitals compared to nonteaching or rural hospitals.
Conclusions:
Infant hospital discharge data can reliably identify markedly preterm or low-birthweight infants but may under-ascertain cases near classification thresholds. Researchers should quantify and adjust for these limitations, for example through quantitative bias analysis or sensitivity analyses to account for misclassification.
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