Karin Rystedt1,2,3,4, Nicolay Jonassen Harbin5, Morten Lindbaek5, Ruta Radzeviciene6, Ronny Gunnarsson2,3,7, Robert Eggertsen2,8, Christopher C Butler9, Alike W van der Velden10, Theo J Verheij10, Pär-Daniel Sundvall2,3,7. 1. Region Västra Götaland, Research and Development Primary Health Care, Research and Development Centre Skaraborg, Skövde, Sweden. 2. Primary Health Care, School of Public Health and Community Medicine, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden. 3. Centre for Antibiotic Resistance Research (CARe), University of Gothenburg, Gothenburg, Sweden. 4. Region Västra Götaland, Närhälsan Södra Ryd Health Care Centre, Skövde, Sweden. 5. Department of General Practice, Antibiotic Center for Primary Care, Institute of Health and Society, University of Oslo, Oslo, Norway. 6. Mano Seimos gydytojas, Klaipeda, Lithuania. 7. Region Västra Götaland, Research and Development Primary Health Care, Research and Development Centre Södra Älvsborg, Borås, Sweden. 8. Region Västra Götaland, Research and Development Primary Health Care, Research and Development Centre Göteborg and Södra Bohuslän, Göteborg, Sweden. 9. Department of Primary Care Health Services, University of Oxford, Radcliffe Observatory Quarter, Oxford, UK. 10. Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, Utrecht, The Netherlands.
Abstract
OBJECTIVE: Identifying influenza A or B as cause of influenza-like illness (ILI) is a challenge due to non-specific symptoms. An accurate, cheap and easy to use biomarker might enhance targeting influenza-specific management in primary care. The aim of this study was to investigate if C-reactive protein (CRP) is associated with influenza A or B, confirmed with PCR testing, in patients presenting with ILI. DESIGN: Cross-sectional study. SETTING: Primary care in Lithuania, Norway and Sweden. SUBJECTS: A total of 277 patients at least 1 year of age consulting primary care with ILI during seasonal influenza epidemics. MAIN OUTCOME MEASURES: Capillary blood CRP analysed as a point-of-care test and detection of influenza A or B on nasopharyngeal swabs in adults, and nasal and pharyngeal swabs in children using PCR. RESULTS: The prevalence of positive tests for influenza A among patients was 44% (121/277) and the prevalence of influenza B was 21% (58/277). Patients with influenza A infection could not be identified based on CRP concentration. However, increasing CRP concentration in steps of 10 mg/L was associated with a significantly lower risk for influenza B with an adjusted odds ratio of 0.42 (0.25-0.70; p<.001). Signs of more severe symptoms like shortness of breath, sweats or chills and dizziness were associated with higher CRP. CONCLUSIONS: There was no association between CRP and influenza A. Increased concentration of CRP was associated with a lower risk for having influenza B, a finding that lacks clinical usefulness. Hence, CRP testing should be avoided in ILI, unless bacterial pneumonia is suspected. Key points Identifying influenza A or B as cause of influenza-like illness (ILI) is a challenge due to non-specific symptoms. There was no association between concentration of CRP and influenza A. Increased concentration of CRP was associated with a lower risk for having influenza B, a finding that lacks clinical usefulness. A consequence is that CRP testing should be avoided in ILI, unless bacterial pneumonia or similar is suspected.
OBJECTIVE: Identifying influenza A or B as cause of influenza-like illness (ILI) is a challenge due to non-specific symptoms. An accurate, cheap and easy to use biomarker might enhance targeting influenza-specific management in primary care. The aim of this study was to investigate if C-reactive protein (CRP) is associated with influenza A or B, confirmed with PCR testing, in patients presenting with ILI. DESIGN: Cross-sectional study. SETTING: Primary care in Lithuania, Norway and Sweden. SUBJECTS: A total of 277 patients at least 1 year of age consulting primary care with ILI during seasonal influenza epidemics. MAIN OUTCOME MEASURES: Capillary blood CRP analysed as a point-of-care test and detection of influenza A or B on nasopharyngeal swabs in adults, and nasal and pharyngeal swabs in children using PCR. RESULTS: The prevalence of positive tests for influenza A among patients was 44% (121/277) and the prevalence of influenza B was 21% (58/277). Patients with influenzaA infection could not be identified based on CRP concentration. However, increasing CRP concentration in steps of 10 mg/L was associated with a significantly lower risk for influenza B with an adjusted odds ratio of 0.42 (0.25-0.70; p<.001). Signs of more severe symptoms like shortness of breath, sweats or chills and dizziness were associated with higher CRP. CONCLUSIONS: There was no association between CRP and influenza A. Increased concentration of CRP was associated with a lower risk for having influenza B, a finding that lacks clinical usefulness. Hence, CRP testing should be avoided in ILI, unless bacterial pneumonia is suspected. Key points Identifying influenza A or B as cause of influenza-like illness (ILI) is a challenge due to non-specific symptoms. There was no association between concentration of CRP and influenza A. Increased concentration of CRP was associated with a lower risk for having influenza B, a finding that lacks clinical usefulness. A consequence is that CRP testing should be avoided in ILI, unless bacterial pneumonia or similar is suspected.
Entities:
Keywords:
C-reactive protein; influenza in humans; point-of-care testing; primary health care; respiratory tract infections
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