Procalcitonin has little value in diagnosing acute appendicitis, with lower diagnostic accuracy than CRP and WBC. However, procalcitonin has greater diagnostic value in identifying complicated appendicitis. Given the imperfect accuracy of these three variables, new markers for improving medical decision-making in patients with suspected appendicitis are highly desirable.

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Background Age-related alterations in the clinical characteristics and performance of severity scoring systems for community-acquired pneumonia (CAP) are unknown. Methods Consecutive patients with CAP presenting to the emergency department were prospectively studied. Patients were classified as younger adults (age 18e64 years), elderly (age 65e84 years) and very old subjects (age $85 years). Clinical characteristics, complications, outcomes and validity of the pneumonia severity index (PSI) and CURB-65 categories were compared across these three age categories. Results Analysis involved 348 (35.3%) younger adult patients, 438 (44.3%) elderly patients and 201 (20.0%) very old patients. Compared with younger adults, elderly and very old patients had a higher burden of comorbidities and a higher incidence of CAP-related complications. The 30-day mortality rate was 5.2% in younger adults, 7.1% in elderly patients and 9.5% in very old patients. The area under the ROC curve (AUCs) for PSI were 0.87 (95% CI 0.77 to 0.97), 0.85 (95% CI 0.803 to 0.897) and 0.69 (95% CI 0.597 to 0.787) and the AUCs for CURB-65 were 0.80 (95% CI 0.67 to 0.93), 0.73 (95% CI 0.65 to 0.82) and 0.60 (95% CI 0.47 to 0.73) in the younger adult, elderly and very old patients, respectively. A modified PSI or CURB-65 excluding the age variable increased the AUC in most age categories. There was no significant effect of age on 30-day mortality after adjusting for other PSI or CURB-65 variables. Conclusion Elderly patients with CAP have more atypical clinical manifestations and worse outcomes. The underperformance of the PSI in elderly patients may be due to the inappropriate weight given to the age variable. A modification of the cut-off point for PSI or CURB-65 to define severe pneumonia may improve the score performance in elderly patients.

Of the three potentially useful markers, PCT had the best positive likelihood ratio and can be used to confirm the diagnosis of bacterial infections in patients with FN. Due to unacceptably high negative likelihood ratio, medical decision for stopping antibiotics based on PCT alone in this high-risk population may not be possible.