TY  - JOUR
A1  - Elias, Johannes
A1  - Heuschmann, Peter U.
A1  - Schmitt, Corinna
A1  - Eckhardt, Frithjof
A1  - Boehm, Hartmut
A1  - Maier, Sebastian
A1  - Kolb-Mäurer, Annette
A1  - Riedmiller, Hubertus
A1  - Müllges, Wolfgang
A1  - Weisser, Christoph
A1  - Wunder, Christian
A1  - Frosch, Matthias
A1  - Vogel, Ulrich
T1  - Prevalence dependent calibration of a predictive model for nasal carriage of methicillin-resistant Staphylococcus aureus
T2  - BMC Infectious Diseases
N2  - Background

Published models predicting nasal colonization with Methicillin-resistant Staphylococcus aureus among hospital admissions predominantly focus on separation of carriers from non-carriers and are frequently evaluated using measures of discrimination. In contrast, accurate estimation of carriage probability, which may inform decisions regarding treatment and infection control, is rarely assessed. Furthermore, no published models adjust for MRSA prevalence.

Methods

Using logistic regression, a scoring system (values from 0 to 200) predicting nasal carriage of MRSA was created using a derivation cohort of 3091 individuals admitted to a European tertiary referral center between July 2007 and March 2008. The expected positive predictive value of a rapid diagnostic test (GeneOhm, Becton & Dickinson Co.) was modeled using non-linear regression according to score. Models were validated on a second cohort from the same hospital consisting of 2043 patients admitted between August 2008 and January 2012. Our suggested correction score for prevalence was proportional to the log-transformed odds ratio between cohorts. Calibration before and after correction, i.e. accurate classification into arbitrary strata, was assessed with the Hosmer-Lemeshow-Test.

Results

Treating culture as reference, the rapid diagnostic test had positive predictive values of 64.8% and 54.0% in derivation and internal validation corhorts with prevalences of 2.3% and 1.7%, respectively. In addition to low prevalence, low positive predictive values were due to high proportion (> 66%) of mecA-negative Staphylococcus aureus among false positive results. Age, nursing home residence, admission through the medical emergency department, and ICD-10-GM admission diagnoses starting with “A” or “J” were associated with MRSA carriage and were thus included in the scoring system, which showed good calibration in predicting probability of carriage and the rapid diagnostic test’s expected positive predictive value. Calibration for both probability of carriage and expected positive predictive value in the internal validation cohort was improved by applying the correction score.

Conclusions

Given a set of patient parameters, the presented models accurately predict a) probability of nasal carriage of MRSA and b) a rapid diagnostic test’s expected positive predictive value. While the former can inform decisions regarding empiric antibiotic treatment and infection control, the latter can influence choice of screening method.
KW  - Methicillin-resistant staphylococcus aureus
KW  - Infection control
KW  - Clinical prediction rule
KW  - Predictive value of tests
KW  - False positive reactions
KW  - Calibration
Y1  - 2013
UR  - https://opus.bibliothek.uni-wuerzburg.de/frontdoor/index/index/docId/9609
UR  - https://nbn-resolving.org/urn:nbn:de:bvb:20-opus-96091
UR  - http://www.biomedcentral.com/1471-2334/13/111
ER  -