C-reactive protein, procalcitonin, clinical pulmonary infection score, and pneumonia severity scores in nursing home acquired pneumonia

Background: Patients with nursing home acquired pneumonia (NHAP) present a distinct group of lower respiratory track infections with different risk factors, clinical presentation, and mortality rates.

Objectives: To evaluate the diagnostic value of clinical pulmonary infection score (CPIS), C-reactive protein, and procalcitonin and to compare the accuracy of pneumonia severity scores (confusion, urea nitrogen, breathing frequency, blood pressure, ≥ 65 y of age [CURB-65]; pneumonia severity index; NHAP index; systolic blood pressure, multilobar involvement, albumin, breathing frequency, tachycardia, confusion, oxygen, arterial pH [SMART-COP]; and systolic blood pressure, oxygen, age > 65 y, breathing frequency [SOAR]) in predicting in-patient mortality from NHAP.

Methods: Nursing home residents admitted to the hospital with acute respiratory illness were enrolled in the study. Subjects were classified as having NHAP (Group A) or other pulmonary disorders (Group B). Clinical, imaging, and laboratory data were assessed to compute CPIS and severity scores. C-reactive protein and procalcitonin were measured by immunonephelometry and immunoassay, respectively.

Results: Fifty-eight subjects were diagnosed with NHAP (Group A) and 29 with other pulmonary disorders (Group B). The mean C-reactive protein ± SD was 16.38 ± 8.6 mg/dL in Group A and 5.2 ± 5.6 mg/dL in Group B (P < .001). The mean procalcitonin ± SD was 1.52 ± 2.75 ng/mL in Group A and 0.24 ± 0.21 ng/mL in Group B (P = .001). The mean CPIS ± SD was 5.4 ± 1.2 in Group A and 2.3 ± 1.5 in Group B (P < .001). At a cutoff value of 0.475 ng/mL, procalcitonin had a sensitivity of 83% and a specificity of 72%. At a cutoff value of 8.05 mg/dL, C-reactive protein had a sensitivity of 81% and a specificity of 79%. Procalcitonin and C-reactive protein levels were significantly higher in Gram-positive NHAP. The in-patient mortality was 17.2% in Group A. Procalcitonin levels were 4.67 ± 5.4 ng/mL in non-survivors and 0.86 ± 0.9 ng/mL in survivors (P < .001). The area under the curve for procalcitonin in predicting in-patient mortality was 0.84 (95% CI 0.70-0.98, P = .001). A procalcitonin level upon admission > 1.1 ng/mL was an independent predictor of in-patient mortality. Of the pneumonia severity scores, CURB-65 showed greater accuracy in predicting in-patient mortality (area under the curve of 0.68, 95% CI 0.53-0.84, P = .06).

Conclusions: CPIS, procalcitonin, and C-reactive protein are reliable for the diagnosis of NHAP. Procalcitonin and CURB-65 are accurate in predicting in-patient mortality in NHAP.