Related Experiment Video
Updated: Jul 17, 2025
Inverse Probability of Treatment Weighting Propensity Score using the Military Health System Data Repository and National Death Index
Published on: January 8, 2020
Comparing the Kids' Inpatient Database and National Inpatient Sample for Pediatric Research
Sarah C McBride1, Matt Hall2, Madelyn G Hall2
1Division of General Pediatrics (SC McBride and JG Berry), Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, Mass.
Insights
Pediatric researchers should note that the Kids' Inpatient Database (KID) and National Inpatient Sample (NIS) show small differences in discharge counts and length of stay (LOS) for common hospitalizations, but larger discrepancies for rare conditions.
Area of Science:
- Pediatric Health Services Research
- Health Informatics
- Biostatistics
Background:
- Pediatric researchers utilize the Agency for Healthcare Research and Quality (AHRQ) Kids' Inpatient Database (KID) and National Inpatient Sample (NIS) for analyzing national pediatric inpatient resource use and outcomes.
- Inherent differences in the sampling designs of KID and NIS may lead to disparate research findings.
Purpose of the Study:
- To compare discharge counts and length of stay (LOS) between the KID and NIS for common and rare pediatric hospital admission reasons.
- To identify potential discrepancies in national estimates derived from these two large pediatric inpatient databases.
Main Methods:
- A retrospective analysis was conducted on 2019 data for children aged 0-20 years from KID and NIS.
- Discharge counts and geometric mean LOS were compared for normal newborns and 331 other admission reasons, categorized by All-Payer Refined Diagnosis Related Groups (APR-DRG) and deciles of annual discharge volume.
- Data were analyzed following AHRQ guidelines for clustering, stratification, and weighting to account for the distinct sampling designs of KID and NIS.
Main Results:
- National estimates for total annual discharge counts showed minimal differences: 0.5% for normal newborns and 3.7% for other admission reasons.
- Discrepancies in discharge counts increased for admission reasons in the two lowest volume deciles (<520 discharges): 9.5% (SD 7.9%) for 200-520 volumes and 41.1% (SD 64.2%) for <200 volumes.
- Length of stay (LOS) differences for these lowest volume deciles were 7.9% (SD 7.1%) and 26.0% (SD 29.3%), respectively.
Conclusions:
- While KID and NIS yield similar results for high-volume pediatric admissions, significant differences emerge for admissions with annual volumes of approximately 500 or less.
- For analyses involving study populations with fewer than 500 discharges, the KID may be the preferred database due to its higher sampling rate of pediatric discharges per hospital.
Objective:
Pediatric researchers use Agency for Healthcare Research and Quality (AHRQ) Kids' Inpatient Database (KID) and National Inpatient Sample (NIS) to analyze the national resource use and outcomes of hospitalized children. Inherent KID-NIS sampling design differences may yield disparate findings. We compared discharge counts and length of stay (LOS) between KID and NIS for common and rare reasons for hospitalization.
Methods:
Retrospective analysis of differences in discharges counts and geometric mean LOS for children ages 0-20 years from KID and NIS in 2019, measured for normal newborns and 331 additional reasons for admission, distinguished by All-Payer Refined Diagnosis Related Groups (APR-DRG) and categorized in deciles by annual discharge volume. We followed AHRQ instructions for data clustering, stratification, and weighting to accommodate the KID and NIS designs, including random samples of 80% and 20% of pediatric discharges, respectively, per hospital.
Results:
KID-NIS differences in national estimates for total annual discharge counts differed by only 0.5% for normal newborns and 3.7% for all other admission reasons in children. KID-NIS differences remained small aside from reasons for admission in the two lowest volume deciles: 9.5% (SD 7.9%) for admission volumes 200-520; 41.1% (SD 64.2%) for volumes <200. KID-NIS LOS differences for these two-lowest volume deciles were 7.9% (SD 7.1%) and 26.0% (SD 29.3%), respectively.
Conclusions:
Although KID-NIS differences in discharge counts and LOS were small for high-volume admissions, the differences increased with reasons for admission that had annual discharge volumes approximately 500 or less. For study populations with discharge counts <500, KID may be preferred, given its higher sampling of discharges per hospital.
Related Concept Videos
02:01Group Design
01:20Comparing the Survival Analysis of Two or More Groups
01:12Statistical Software for Data Analysis and Clinical Trials
01:12Analysis of Population Pharmacokinetic Data