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Background: C-reactive protein (CRP) has been proposed as a biomarker for pulmonary exacerbation (PEx) diagnosis and treatment response. CRP >75mg/L has been associated with increased risk of PEx treatment failure. We have analyzed CRP measures as biomarkers for clinical response during the STOP2 PEx study (NCT02781610)., Methods: CRP measures were collected at antimicrobial treatment start (V1), seven to 10 days later (V2), and two weeks after treatment end (V3). V1 log 10 CRP concentrations and log 10 CRP change from V1 to V3 correlations with clinical responses (changes in lung function and symptom score) were assessed by least squares regression. Odds of intravenous (IV) antimicrobial retreatment within 30 days and future PEx hazard associated with V1 and V3 CRP concentrations and V1 CRP >75 mg/L were studied by adjusted logistic regression and proportional hazards modeling, respectively., Results: In all, 951 of 982 STOP2 subjects (92.7%) had CRP measures at V1. V1 log 10 CRP varied significantly by V1 lung function subgroup, symptom score quartile, and sex, but not by age subgroup. V1 log 10 CRP correlated moderately with log 10 CRP change at V3 (r 2 =0.255) but less so with lung function (r 2 =0.016) or symptom (r 2 =0.031) changes at V3. Higher V1 CRP was associated with greater response. CRP changes from V1 to V3 only weakly correlated with lung function (r 2 =0.061) and symptom (r 2 =0.066) changes. However, V3 log 10 CRP was associated with increased odds of retreatment (P = .0081) and future PEx hazard (P = .0114)., Discussion: Despite consistent trends, log 10 CRP change was highly variable with only limited utility as a biomarker of PEx treatment response., Competing Interests: Declaration of Competing Interest The authors claim no financial conflicts of interest related to this work., (Copyright © 2021 European Cystic Fibrosis Society. Published by Elsevier B.V. All rights reserved.)

Background: In the STOP2 (Standardized Treatment of Pulmonary Exacerbations-2) study, intravenous (IV) antimicrobial treatment duration for adults with cystic fibrosis (CF) experiencing pulmonary exacerbations (PEx) was determined based on initial treatment response. The impact of home vs hospital care remains an important clinical question in CF. Our hypothesis was that STOP2 participants treated at home would have less improvement in lung function compared to those treated in the hospital., Methods: Treating clinicians determined PEx treatment location, which was a stratification factor for STOP2 randomization. Lung function, weight, and symptom recovery were evaluated by treatment location. Propensity scores and inverse probability treatment weighting were used to test for differences in clinical response by treatment location., Results: In all, 33% of STOP2 participants received IV antimicrobials in the hospital only, 46% both in the hospital and at home, and 21% at home only. Mean (95% CI) ppFEV 1 improvement was significantly (p < 0.05) lower for those treated at home only, 5.0 (3.5, 6.5), compared with at home and in the hospital, 7.0 (5.9, 8.1), and in the hospital only, 8.0 (6.7, 9.4). Mean weight (p < 0.001) and symptom (p < 0.05) changes were significantly smaller for those treated at home only compared to those treated in the hospital only., Conclusions: Compared to PEx treatment at home only, treatment in the hospital was associated with greater mean lung function, respiratory symptom, and weight improvements. The limitations of home IV therapy should be addressed in order to optimize outcomes for adults with CF treated at home., (Copyright © 2021. Published by Elsevier B.V.)