The added diagnostic value of five different C-reactive protein point-of-care test devices in detecting pneumonia in primary care: A nested case-control study.

Background: The results obtained from various point-of-care (POC) test devices for estimating C-reactive protein (CRP) levels in a laboratory setting differ when compared to a laboratory reference test. We aimed to determine whether such differences meaningfully affect the accuracy and added diagnostic value in predicting radiographic pneumonia in adults presenting with acute cough in primary care.

Methods: A nested case control study of adult patients presenting with acute cough in 12 different European countries (the Genomics to combat Resistance against Antibiotics in Community-acquired LRTI in Europe [GRACE] Network). Venous blood samples from 100 patients with and 100 patients without pneumonia were tested with five different POC CRP tests and a laboratory analyzer. Single test accuracy values and the added value of CRP to symptoms and signs were calculated.

Results: Single test accuracy values showed similar results for all five POC CRP tests and the laboratory analyzer. The area under the curve of the different POC CRP tests and the laboratory analyzer (range 0.79-0.80) were all comparable and higher than the clinical model without CRP (0.70). Multivariable odds ratios were the same (1.2) for all CRP tests.

Conclusions: Five POC CRP test devices and the laboratory analyzer performed with similar accuracy in detecting pneumonia both as single test, and when used in addition to clinical findings. Variability in results obtained from standard CRP laboratory and POC test devices do not translate into clinically relevant differences when used for prediction of pneumonia in patients with acute cough in primary care.