Skip to main page content
U.S. flag

An official website of the United States government

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2012 Mar 27:12:245.
doi: 10.1186/1471-2458-12-245.

Lessons from a one-year hospital-based surveillance of acute respiratory infections in Berlin- comparing case definitions to monitor influenza

Matthias Nachtnebel  1 , Benedikt Greutelaers, Gerhard Falkenhorst, Pernille Jorgensen, Manuel Dehnert, Brunhilde Schweiger, Christian Träder, Silke Buda, Tim Eckmanns, Ole Wichmann, Wiebke Hellenbrand
Affiliations

Lessons from a one-year hospital-based surveillance of acute respiratory infections in Berlin- comparing case definitions to monitor influenza

Matthias Nachtnebel et al. BMC Public Health. .

Abstract

Background: Surveillance of severe acute respiratory infections (SARI) in sentinel hospitals is recommended to estimate the burden of severe influenza-cases. Therefore, we monitored patients admitted with respiratory infections (RI) in 9 Berlin hospitals from 7.12.2009 to 12.12.2010 according to different case definitions (CD) and determined the proportion of cases with influenza A(H1N1)pdm09 (pH1N1). We compared the sensitivity and specificity of CD for capturing pandemic pH1N1 cases.

Methods: We established an RI-surveillance restricted to adults aged ≤ 65 years within the framework of a pH1N1 vaccine effectiveness study, which required active identification of RI-cases. The hospital information-system was screened daily for newly admitted RI-patients. Nasopharyngeal swabs from consenting patients were tested by PCR for influenza-virus subtypes. Four clinical CD were compared in terms of capturing pH1N1-positives among hospitalized RI-patients by applying sensitivity and specificity analyses. The broadest case definition (CD1) was used for inclusion of RI-cases; the narrowest case definition (CD4) was identical to the SARI case definition recommended by ECDC/WHO.

Results: Over the study period, we identified 1,025 RI-cases, of which 283 (28%) met the ECDC/WHO SARI case definition. The percentage of SARI-cases among internal medicine admissions decreased from 3.2% (calendar-week 50-2009) to 0.2% (week 25-2010). Of 354 patients tested by PCR, 20 (6%) were pH1N1-positive. Two case definitions narrower than CD1 but -in contrast to SARI- not requiring shortness of breath yielded the largest areas under the Receiver-Operator-Curve. Heterogeneity of proportions of patients admitted with RI between hospitals was significant.

Conclusions: Comprehensive surveillance of RI cases was feasible in a network of community hospitals. In most settings, several hospitals should be included to ensure representativeness. Although misclassification resulting from failure to obtain symptoms in the hospital information-system cannot be ruled out, a high proportion of hospitalized PCR-positive pH1N1-patients (45%) did not fulfil the SARI case-definition that included shortness of breath or difficulty breathing. Thus, to assess influenza-related disease burden in hospitals, broader, alternative case definitions should be considered.

PubMed Disclaimer

Figures

Figure 1
Figure 1
Flowchart of case definitions (CD) for hospitalized respiratory infections. To be included as a case in the hospital-based surveillance of acute respiratory infections in Berlin, 2009/10, patients had to fulfil criteria of the broadest case definition (CD1). All CD1 who did not meet the CD4 (SARI) criteria were classified as CD1b. CD2 and CD3 fulfilled clinical criteria only and excluded those where clinical criteria were not fully met but a physician's (suspected) diagnosis of RI in the chart led to inclusion. The smallest subsample of CD1 were cases fulfilling CD4 criteria (SARI as defined by ECDC/WHO).
Figure 2
Figure 2
Incidence of hospitalized respiratory infections fulfilling criteria for CD1b and CD4 as a percentage of internal medicine ward admissions in the study hospitals per calendar week. Weekly incidences are shown together with predicted incidences and 95%CI according to Poisson regression. All pH1N1 cases notified in Berlin through the national routine surveillance system, 2009-2010 are shown for comparison.
Figure 3
Figure 3
Incidence of respiratory infections fulfilling criteria for CD1 admitted to intensive care units (ICU) as a percentage of all admissions to ICU per calendar week. Weekly incidences are shown together with predicted incidences and 95%CI according to Poisson regression. All pH1N1 cases notified in Berlin through the national routine surveillance system, 2009-2010 are shown for comparison.
Figure 4
Figure 4
Receiver Operator Curve (ROC) comparing the capability of different case definitions (CD) for hospitalized respiratory infections (RI) to capture cases of influenza A/H1N1 2009 (pH1N1). Areas under the ROC curve for CD2, CD3 and CD4 using pH1N1 PCR results as the gold standard for the overall study period (left) and the period with significant pH1N1 in Berlin (right). Data based on cases of respiratory infections hospitalized in the participating hospitals and tested for influenza, Berlin, December 2009 to December 2010. pH1N1 negative cases included only if period between symptom onset and nasopharyngeal swab ≤ 7 days.
See this image and copyright information in PMC

Similar articles

See all similar articles

Cited by

See all "Cited by" articles

References

    1. Buda S, Kopke K, Haas W. Epidemiological characteristics of the influenza pandemic (H1N1) 2009 in Germany based on the mandatory notification of cases. Bundesgesundheitsblatt Gesundheitsforschung Gesundheitsschutz. 2010;53(12):1223–1230. doi: 10.1007/s00103-010-1158-0. - DOI - PubMed
    1. Arbeitsgemeinschaft Influenza (AGI) Bericht zur Epidemiologie der Influenza in Deutschland Saison 2009/10. 2010.
    1. Rothberg MB, Haessler SD, Brown RB. Complications of viral influenza. Am J Med. 2008;121(4):258–264. doi: 10.1016/j.amjmed.2007.10.040. - DOI - PMC - PubMed
    1. Rothberg MB, Haessler SD. Complications of seasonal and pandemic influenza. Crit Care Med. 2010;38(4 Suppl):e91–97. - PubMed
    1. Baker MG, Wilson N, Huang QS, Paine S, Lopez L, Bandaranayake D, Tobias M, Mason K, Mackereth GF, Jacobs M, Thornley C, Roberts S, McArthur C. Pandemic influenza A(H1N1)v in New Zealand: the experience from April to August 2009. Euro Surveill. 2009;14(34) pii = 19319 http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=19319. - PubMed

Publication types

MeSH terms

Substances