Diagnostic value of procalcitonin in acutely hospitalized elderly patients

The aim of this study was to evaluate procalcitonin as an adjunct to diagnose bacterial infections in older patients. One hundred seventy-two patients admitted to an acute-care geriatric unit during a 6-month period were prospectively included, 39 of them with an invasive bacterial infection. The best cut-off value to rule in a bacterial infection was 0.51 microg/l with sensitivity 64% and specificity 94%. The best cut-off value to rule out a bacterial infection was 0.08 microg/l with sensitivity 97% and specificity 20%. Procalcitonin was inconclusive (between 0.08 and 0.51 microg/l) for 112 admissions. Procalcitonin over 0.51 microg/l was useless 22 times out of 33 (infection already ruled in on clinical grounds) and misleading in eight of the 11 remaining cases (no infection). Procalcitonin below 0.08 microg/l was useless 23 times out of 27 (infection already ruled out on clinical grounds) and misleading in one of the four remaining cases (infection). Despite a good overall diagnostic accuracy, the clinical usefulness of PCT to diagnose invasive bacterial infections in elderly patients hospitalized in an acute geriatric ward appears to be very limited.