Background: The urinary pneumococcal antigen (PnAG) test is widely used in the setting of community acquired pneumonia (CAP). Data regarding the impact of the test on antibiotic prescriptions are lacking.
Method: The study population consisted of patients with suspicion of CAP in whom PnAG testing was performed. From November 2007 until August 2008, all patients in whom pneumococcal antigen testing (Binax Now®, PnAG) was performed were evaluated. In a second period, from September 2008 until March 2009, we stopped PnAG testing in our institution. We compared the microbiological verification procedures, antibiotic prescription and the final diagnosis of CAP of the first period (n = 139) against the second period (n = 147).
Results: Only 139/188 patients in whom PnAG was performed had CAP. Of these, 22 (15%) were PnAG positive. In 11/22 patients, the diagnosis of pneumococcal pneumonia was additionally confirmed by positive blood and/or sputum culture. In only 6 of the remaining 11 patients, antibiotic treatment was changed as a consequence of the positive PnAG test. In cases of blood culture positive and in sputum positive pneumococcal pneumonia, only 8/13 (61%) and 3/15 (20%) were PnAG positive, respectively. The costs of the PnAG test were 188 × 42 CHF (in total 7,896 CHF) and no cost savings were observed. Neither with empiric nor with consequently prescribed antibiotic treatment was a difference found between the PnAG and control period.
Conclusion: In our patient population, the routine Binax Now® PnAG testing did not lead to cost savings or narrowing of antibiotic prescriptions. Thus, PnAG testing should be limited to cases of diagnostic uncertainty where blood or sputum cultures are negative or not available.