Clinical Pathway Based on Procalcitonin Levels for the Management of Community-acquired Pneumonia in Outpatients

A clinical protocol was developed in collaboration with the hospital's Emergency Department for the management of adult outpatients with community-acquired pneumonia (CAP). Patients are assigned to 2 treatment categories according to the plasma procalcitonin (PCT) values.

Treatment assignment:

1. PCT<0.5 ng/ml: azithromycin, 500 mg/day orally for 5 days
2. PCT≥0.5ng/ml: levofloxacin, 500 mg/day orally for 7 days

Laboratory and microbiological studies:

In the ED, patients with signs and symptoms of pneumonia have a blood sample collected for routine biochemical and hematological determinations, and PCT concentration measurement.

Rapid testing for the determination of PCT are performed with BRAHMS PCT-Q, an immunochromatografic test for the semi-quantitative detection of PCT in serum (BRAHMS GmbH, 16761 Hennigsdorf, Germany). PCT concentration ranges are the following: <0.5 ng/ml; ≥ 0.5 ng/ml; ≥2 ng/ml; ≥10 ng/ml.

The etiological diagnostic workup includes obtaining sputum samples from patients with productive cough, and a urine sample for detection of S. pneumoniae and Legionella pneumophila serogroup 1 antigens by immunochromatographic assays (Binax NOW, Alere Healthcare SLU, Spain). Only qualified sputum samples, as defined according to standard criteria (presence of >25 WBC and <10 squamous cells per low-power magnification field [x10]) are evaluated. Serum samples (obtained during the acute stage of illness and 4 weeks later) are collected and frozen at -80ºC for ulterior serological testing. An indirect chemiluminescent immunoassay (VirClia® Monotest, Vircell, S.L., Granada, Spain) is performed to detect IgG antibodies against Mycoplasma pneumoniae, Chlamydophila pneumoniae, Legionella pneumophila and Coxiella burnetii. Calculation of cutoff values and interpretation of the results are performed in accordance with the instructions of the manufacturer. The diagnostic criteria are either a seroconversion (index value from negative to positive) or a significant increase in the index value (≥threefold) in paired samples. All assays are performed and analyzed blindly by the same person.

Follow-up and outcome measures:

After treatment has been assigned, patients are referred to the outpatients clinic, where they are seen within the following 24 hours (Visit 2). A phone visit (Visit 3) is scheduled on day 7, and the last programmed visit on day 30 at the clinic (Visit 4). Patients are instructed to visit the outpatients' clinic if their clinical status worsens or fever persists more than 48 hours after the first visit. Cure is defined as an improvement or lack of progression of baseline radiographic findings at the end of therapy (EOT) and resolution of signs, including chest X-Ray, and symptoms of pneumonia at visit 4. Failure is defined as persistence or progression of signs and symptoms or progression of radiological signs of pneumonia at EOT, persistent infiltrate on X-Ray at visit 4, and initiation within 2 calendar days of the initial antibiotic therapy of a different potentially effective antibiotic, death on or after day 3 attributable to primary infection, or relapsed infection at visit 4. Antibiotic change requirement due to toxicity, and need for hospital admission is also recorded.

In addition to the short-term outcome, the long-term (3-year) outcome of the patients is assessed through a structured telephone interview.