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Influenza Other Respir Viruses. 2018 Jan;12(1):122-131. doi: 10.1111/irv.12495. Epub 2018 Feb 15.

Estimated rates of influenza-associated outpatient visits during 2001-2010 in 6 US integrated healthcare delivery organizations.

Author information

1
Centers for Disease Control & Prevention, Atlanta, GA, USA.
2
Marshfield Clinic Research Foundation, Marshfield, WI, USA.
3
Kaiser Permanente Vaccine Study Center, Oakland, CA, USA.
4
Department of Research and Evaluation, Kaiser Permanente Southern California, Pasadena, CA, USA.
5
Group Health Research Institute, Seattle, WA, USA.
6
Institute for Health Research, Kaiser Permanente, Denver, CO, USA.
7
Center for Health Research, Kaiser Permanente Northwest, Portland, OR, USA.

Abstract

BACKGROUND:

Population-based estimates of influenza-associated outpatient visits including both pandemic and interpandemic seasons are uncommon. Comparisons of such estimates with laboratory-confirmed rates of outpatient influenza are rare.

OBJECTIVE:

To estimate influenza-associated outpatient visits in 6 US integrated healthcare delivery organizations enrolling ~7.7 million persons.

METHODS:

Using negative binomial regression methods, we modeled rates of influenza-associated visits with ICD-9-CM-coded pneumonia or acute respiratory outpatient visits during 2001-10. These estimated counts were added to visits coded specifically for influenza to derive estimated rates. We compared these rates with those observed in 2 contemporaneous studies recording RT-PCR-confirmed influenza outpatient visits.

RESULTS:

Outpatient rates estimated with pneumonia visits were 39 (95% confidence interval [CI], 30-70) and 203 (95% CI, 180-240) per 10 000 person-years, respectively, for interpandemic and pandemic seasons. Corresponding rates estimated with respiratory visits were 185 (95% CI, 161-255) and 542 (95% CI, 441-823) per 10 000 person-years. During the pandemic, children aged 2-17 years had the largest increase in rates (when estimated with pneumonia visits, from 64 [95% CI, 50-121] to 381 [95% CI, 366-481]). Rates estimated with pneumonia visits were consistent with rates of RT-PCR-confirmed influenza visits during 4 of 5 seasons in 1 comparison study. In another, rates estimated with pneumonia visits during the pandemic for children and adults were consistent in timing, peak, and magnitude.

CONCLUSIONS:

Estimated rates of influenza-associated outpatient visits were higher in children than adults during pre-pandemic and pandemic seasons. Rates estimated with pneumonia visits plus influenza-coded visits were similar to rates from studies using RT-PCR-confirmed influenza.

KEYWORDS:

electronic health records; human; influenza; office visits; statistical models

PMID:
28960732
PMCID:
PMC5818343
DOI:
10.1111/irv.12495
[Indexed for MEDLINE]
Free PMC Article

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