P3A283: Using Syndromic Surveillance Data for Surveillance of Unintentional and Undetermined Intent Drowning in a Large Metropolitan Area

Background: The CDC adapted a drowning syndromic surveillance definition for use in National Syndromic Surveillance Program (NSSP) data. However, the accuracy of the syndrome in capturing emergency department (ED) and urgent care (UCC) visits [collectively termed Syndromic Surveillance (SS) visits], and its use in drowning surveillance is unknown. We aimed to determine the percentages of true-positive unintentional and undetermined intent drowning (UUID) cases for all ages in a large metropolitan area based on all cases captured by this definition. A secondary aim was to describe the burden and injury trends of UUID syndromic surveillance visits.

Methods: We applied the CDC definition for drowning to data available in NSSP for the 8-county metropolitan Houston area for the years 2018-2022. Data were analyzed after querying the dataset for ICD-10-CM codes for UUID cases and manually reviewing the text describing the chief complaint and discharge diagnosis for UUID SS visits. To calculate the percentage of true-positives, we divided the number of UUID cases by the total visits captured by the syndromic definition for drowning. Drowning rates comprised SS visits for UUID divided by the total number of SS visits and multiplied by 100,000. These were calculated by gender, ethnicity and minority status.

Results: There were 24,742,818 (ED: 23,870,676; UCC: 872,142) SS visits captured by the NSSP for metropolitan Houston between 2018 to 2022. During the same period, there were 2,759 SS visits for UUID (Mean rate:11.15 UUID SS visits/100,000 SS visits. There were 2,019 cases (72.5%) with ICD-10-CM codes for drowning; 2,015 (99.8%) were classified as UUID. Of the remaining 740 cases with no ICD-10-CM codes, there were 690 (93.2%) cases with a chief complaint or discharge diagnosis text indicating “drowning” or “submersion” or “underwater” or “inhaled water” or “swallowed water” in relation to contact with a body of water and/or specific misspellings. Among all 2,759 visits classified as drowning based on the syndromic surveillance definition for drowning, there were 2,705 (98.0%) cases classified as Yes (true-positive) UUID and 54 (2.0%) classified as “No”.
UUID SS visits were lowest during 2020 (9.6/100,000 SS visits). Males and minority groups constituted 48% and 38% of SS visits for UUID respectively. Children aged 0-17 years comprised 79.3% of SS visits for UUID. UUID SS rates for minority groups (11.75/100,000 SS visits) and non-minority groups (11.81/100,000 SS visits) were similar. UUID SS rates for males (13.7/100,000 SS visits) were higher than females (8.5/100,000 SS visits); and higher for non-Hispanics (12.3/100,000 SS visits) compared to Hispanic persons (10.4/100,000 SS visits).

Conclusion: Syndromic surveillance data are a novel source for conducting drowning surveillance in a large metropolitan region. The CDC’s syndromic surveillance definition for drowning accurately captures nearly all SS visits of drowning victims who present to the ED or UCC.