***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: CONTEXT In previous smaller trials , a procalcitonin ( PCT ) algorithm reduced antibiotic use in patients with lower respiratory tract infections ( LRTIs ) . OBJECTIVE To examine whether a PCT algorithm can reduce antibiotic exposure without increasing the risk for serious adverse outcomes . DESIGN , SETTING , AND PATIENTS A multicenter , noninferiority , r and omized controlled trial in emergency departments of 6 tertiary care hospitals in Switzerl and with an open intervention of 1359 patients with mostly severe LRTIs r and omized between October 2006 and March 2008 . INTERVENTION Patients were r and omized to administration of antibiotics based on a PCT algorithm with predefined cutoff ranges for initiating or stopping antibiotics ( PCT group ) or according to st and ard guidelines ( control group ) . Serum PCT  was measured locally in each hospital and instructions were Web-based . MAIN OUTCOME MEASURES Noninferiority of the composite adverse outcomes of death , intensive care unit admission , disease-specific complications , or recurrent infection requiring antibiotic treatment within 30 days , with a predefined noninferiority boundary of 7.5 % ; and antibiotic exposure and adverse effects from antibiotics . RESULTS The rate of overall adverse outcomes was similar in the PCT and control groups ( 15.4 % [ n = 103 ] vs 18.9 % [ n = 130 ] ; difference , -3.5 % ; 95 % CI , -7.6 % to 0.4 % ) . The mean duration of antibiotics exposure in the PCT vs control groups was lower in all patients ( 5.7 vs 8.7 days ; relative change , -34.8 % ; 95 % CI , -40.3 % to -28.7 % ) and in the subgroups of patients with community-acquired pneumonia ( n = 925 , 7.2 vs 10.7 days ; -32.4 % ; 95 % CI , -37.6 % to -26.9 % ) , exacerbation of chronic obstructive pulmonary disease ( n = 228 , 2.5 vs 5.1 days ; -50.4 % ; 95 % CI , -64.0 % to -34.0 % ) , and acute bronchitis ( n = 151 , 1.0 vs 2.8 days ; -65.0 % ; 95 % CI , -84.7 % to -37.5 % ) . Antibiotic-associated adverse effects were less frequent in the PCT group ( 19.8 % [ n = 133 ] vs 28.1 % [ n = 193 ] ; difference , -8.2 % ; 95 % CI , -12.7 % to -3.7 % ) . CONCLUSION In patients with LRTIs , a strategy of PCT guidance compared with st and ard guidelines result ed in similar rates of adverse outcomes , as well as lower rates of antibiotic exposure and antibiotic-associated adverse effects . TRIAL REGISTRATION is rct n.org Identifier : IS RCT N95122877 Background : Biological markers as an expression of systemic inflammation have been recognised as useful for evaluating the host response in community-acquired pneumonia ( CAP ) . The objective of this study was to evaluate whether the biological markers procalcitonin ( PCT ) and C-reactive protein ( CRP ) might reflect stability after 72 h of treatment and the absence of subsequent severe complications . Methods : A prospect i ve cohort study was performed in 394 hospitalised patients with CAP . Clinical stability was evaluated using modified Halm ’s criteria : temperature ⩽37.2 ° C ; heart rate ⩽100 beats/min ; respiratory rate ⩽24 breaths/min ; systolic blood pressure ⩾90 mm Hg ; oxygen saturation ⩾90 % ; or arterial oxygen tension ⩾60 mm Hg . PCT and CRP levels were measured on day 1 and after 72 h. Severe complications were defined as mechanical ventilation , shock and /or intensive care unit ( ICU ) admission , or death after 72 h of treatment . Results : 220 patients  achieved clinical stability at 72 h and had significantly lower levels of CRP ( 4.2 vs 7 mg/dl ) and of PCT ( 0.33 vs 0.48 ng/ml ) . Regression logistic analyses were performed to calculate several areas under the ROC curve ( AUC ) to predict severe complications . The AUC for clinical stability was 0.77 , 0.84 when CRP was added ( p = 0.059 ) and 0.77 when PCT was added ( p = 0.45 ) . When clinical stability was achieved within 72 h and marker levels were below the cut-off points ( 0.25 ng/ml for PCT and 3 mg/dl for CRP ) , no severe complications occurred . Conclusions : Low levels of CRP and PCT at 72 h in addition to clinical criteria might improve the prediction of absence of severe complications Background : The induction of C-reactive Protein ( CRP ) may be attenuated by corticosteroids , whereas Procalcitonin ( PCT ) appears to be unaltered . We investigated , whether in community-acquired pneumonia ( CAP ) a combined antibiotic-corticosteroid therapy may actually lead to different slopes of decline of these inflammatory markers . Patients and Methods : We studied the slopes of decline of PCT and CRP serum levels during 7 consecutive days as well as clinical parameters in a group of patients with CAP on or off corticosteroids . Patients with underlying COPD received systemic corticosteroids ( n = 10 ) , while non- COPD patients ( n = 10 ) presenting with CAP alone formed the control group . All patients were treated with antibiotics . Results : At baseline , relevant clinical and laboratory characteristics of the two groups were similar . Regarding the decreasing shapes of the curves from PCT and CRP , no significant differences were found ( p-value = 0.48 for the groups for CRP , respectively 0.64 for PCT ) . All patients showed an uneventful recovery . Conclusion : In patients with COPD and CAP , the time courses over 7 days of PCT and CRP showed a nearly parallel decline compared to non- COPD patients with CAP . Contrary to the induction phase , corticosteroids do not modify the time-dependent decay of PCT and CRP when the underlying infectious disease ( CAP ) is adequately treated Objectives Procalcitonin ( PCT ) kinetics is a good prognosis marker in infectious diseases , but few studies of community-acquired pneumonia ( CAP ) have been performed in intensive care units ( ICU ) . We analyzed the relationship between PCT kinetics and outcome in ICU patients with severe CAP . Design and setting Prospect i ve observational study in a 16-bed university hospital ICU . Patients 100 critically ill patients with community-acquired pneumonia . Measurements and results Median PCT  was 5.2 ng/ml on day 1 and 2.9 ng/ml on day 3 . It increased from day 1 to day 3 in nonsurvivors but decreased in survivors . In multivariate analysis four variables were associated with death : invasive ventilation ( odds ratio 10− ) , multilobar involvement ( 5.6− ) , LOD score ( 6.9− ) , and PCT increase from day 1 to day 3 ( 4.5− ) . In intubated patients with a PCT level below 0.95 ng/ml on day 3 the survival rate was 95 % . Conclusion Increased PCT from day 1 to day 3 in severe CAP is a poor prognosis factor . A PCT level less than 0.95 ng/ml on day 3 in intubated patients is associated with a favorable outcome RATIONALE In patients with community-acquired pneumonia , guidelines recommend antibiotic treatment for 7 to 21 d. Procalcitonin is elevated in bacterial infections , and its dynamics have prognostic implication s. OBJECTIVE To assess procalcitonin guidance for the initiation and duration of antibiotic therapy in community-acquired pneumonia . METHODS In a r and omized intervention trial , 302 consecutive patients with suspected community-acquired pneumonia were included . Data were assessed at baseline , after 4 , 6 , and 8 d , and after 6 wk . The control group ( n = 151 ) received antibiotics according to usual practice . In the procalcitonin group ( n = 151 ) , antibiotic treatment was based on serum procalcitonin concentrations as follows : strongly discouraged , less than 0.1 microg/L ; discouraged , less than 0.25 microg/L ; encouraged , greater than 0.25 microg/L ; strongly encouraged , greater than 0.5 microg/L. The primary endpoint was antibiotic use ; secondary endpoints were measures of clinical , laboratory , and radiographic outcome . RESULTS At baseline , both groups were similar regarding clinical , laboratory , and microbiology characteristics , and Pneumonia Severity Index .  Procalcitonin guidance reduced total antibiotic exposure ( relative risk , 0.52 ; 95 % confidence interval , 0.48 - 0.55 ; p < 0.001 ) , antibiotic prescriptions on admission ( 85 vs. 99 % ; p < 0.001 ) , and antibiotic treatment duration ( median , 5 vs. 12 d ; p < 0.001 ) compared with patients treated according to guidelines . After adjustment for Pneumonia Severity Index , the hazard ratio of antibiotic discontinuation was higher in the procalcitonin group than in the control group ( 3.2 ; 95 % confidence interval , 2.5 to 4.2 ) . Outcome was similar in both groups , with an overall success rate of 83 % . CONCLUSIONS Procalcitonin guidance substantially reduces antibiotic use in community-acquired pneumonia . These findings may have important clinical and public health implication BACKGROUND Acute respiratory tract infections are the most common reason for antibiotic therapy in primary care despite their mainly viral etiology . A laboratory test measuring procalcitonin levels in blood specimens was suggested as a tool to reduce unnecessary prescribing of antibiotics . We consider whether antibiotic therapy guided by procalcitonin reduces the use of antibiotics without increasing the restrictions experienced by patients by more than 1 day . METHODS Fifty-three primary care physicians recruited 458 patients , each patient with an acute respiratory tract infection and , in the physician 's opinion , in need of antibiotics .  Patients were central ly r and omized to either a procalcitonin-guided approach to antibiotic therapy or to a st and ard approach . For patients r and omized to procalcitonin-guided therapy , the use of antibiotics was more or less strongly discouraged ( procalcitonin level , < or = 0.1 or < or = 0.25 microg/L , respectively ) or recommended ( procalcitonin level , > 0.25 microg/L ) . Follow-up data were collected at 7 days by treating physicians and at 14 and 28 days by blinded interviewers . RESULTS Adjusted for baseline characteristics , the mean increase at 14 days in days in which activities were restricted was 0.14 with procalcitonin-guided therapy ( 95 % confidence interval [ CI ] , -0.53 to 0.81 days ) , which met our criterion of an increase in days in which activities were restricted by no more than 1 day . With procalcitonin-guided therapy , the antibiotic prescription rate was 72 % lower ( 95 % CI , 66%-78 % ) than with st and ard therapy . Both approaches led to a similar proportion of patients reporting symptoms of ongoing or relapsing infection at 28 days ( adjusted odds ratio , 1.0 [ 95 % CI , 0.7 - 1.5 ] ) . CONCLUSIONS As an adjunct to guidelines , procalcitonin-guided therapy markedly reduces antibiotic use for acute respiratory tract infections in primary care without compromising patient outcome . In practice , this could be achieved with 1 to 2 procalcitonin measurements in patients for whom the physician intends to prescribe antibiotics STUDY OBJECTIVES To evaluate the usefulness of procalcitonin serum levels as a predictor of etiology and prognosis in adult patients with community-acquired pneumonia ( CAP ) when they are stratified according to severity . DESIGN One-year , population -based , prospect i ve study . SETTING University teaching hospital . PATIENTS All adult patients who received a diagnosis of CAP throughout the study period . INTERVENTIONS AND MEASUREMENTS An extensive noninvasive microbiological workup was performed . In patients who gave informed consent , a blood sample was collected at the time the diagnosis of CAP was established to measure biological markers .  Procalcitonin levels were measured by a commercially available monoclonal immunoluminometric assay ( limit of detection , 0.1 microg/L ) . Patients were classified according to microbial diagnosis , Patients Outcome Research Team pneumonia severity index ( PSI ) , and outcome measures , and procalcitonin levels were compared among groups . RESULTS Of 240 patients who received a diagnosis of CAP during the study period ,  procalcitonin  concentrations were measured in 185 patients ( 77.1 % ) . Levels were higher in patients with high 
    Output:
    
RESULTS The most thoroughly studied topic is the prediction of complications and death during hospital stay .
PCT has predictive properties comparable to those of the Pneumonia Severity Index and the CURB65 scoring systems , and it may represent an addition to these indices .
Furthermore , PCT levels may indicate aetiology as patients with typical bacterial infection have higher PCT levels than patients with atypical and viral aetiologies .
The literature also indicates that PCT can distinguish CAP from asthma and acute exacerbation of chronic obstructive pulmonary disease .
Several studies and a meta- analysis have shown that administration of antibiotics according to a PCT algorithm in a hospital setting reduced the use of antibiotics with no evidence of an increased risk .