SummaryBackground The clinical utility of serum periostin as a type 2 biomarker in asthma is limited by lack of reference range values derived from a population without respiratory disease. Objective To derive age-and sex-related reference intervals for serum periostin from an adult population without asthma or COPD. Methods Serum periostin levels were measured in 480 individuals, comprising 60 female and 60 male adults in each of the 18-to 30-year, 31-to 45-year, 46-to 60-year and 61-to 75-year age groups. Key exclusion criteria included a doctor's diagnosis of asthma, chronic bronchitis or COPD, and a history of wheezing or use of respiratory inhalers in the last 12 months. The distribution of periostin and logarithm-transformed periostin levels was derived, and 90% confidence intervals for an individual prediction were calculated. Results The distribution of serum periostin was right skewed with a mean (SD) periostin of 51.2 (11.9) ng/mL, median (IQR) 50.1 (43.1 to 56.9) ng/mL and range 28.1 to 136.4 ng/ mL. There was no association between logarithm periostin and age or sex, although levels were low in current smokers. The 90% confidence limits for periostin were 35.0 and 71.1 ng/mL. Conclusions and Clinical Relevance Serum periostin levels in adults without asthma or COPD are similar to those in adults with asthma. Serum periostin measurements do not need to be adjusted to take account of a patient's age or sex, although levels are lower in current smokers. Reference values for serum periostin levels in adults without asthma or COPD are provided.

Braithwaite have all received grants from Genentech. C. Holweg is an employee of Genentech, a member of the Roche group. J. Matthews is employed by Genentech, a member of the Roche group, and is a named inventor on a pending patent application assigned to his employer relating to subject matter in the manuscript. R. Beasley reports grants from Genentech during the conduct of the study and personal fees from the Health Research Council of New Zealand, GlaxoSmithKline, AstraZeneca, and Novartis and grants from AstraZeneca, Chiesi, Cephalon, Genentech, Novartis, Sanofi Aventis, outside the submitted work. M. Weatherall declares that he has no conflicts of interest.

BackgroundWe aimed to determine the effect of sampling time during the day on serum periostin levels in adult participants with and without asthma.MethodsSerum periostin was measured at 2-h intervals from 0800 to 1800 h in 16 adult participants with stable asthma prescribed inhaled corticosteroid and long-acting beta-agonist therapy, and in 16 otherwise healthy participants without asthma. Mixed linear models were used to compare time zero (08:00 h) with subsequent measurement time for serum periostin for both groups.ResultsIn both asthma and non-asthma, the mean (SD) serum periostin levels continuously reduced during the day from 53.5 (13.6) ng/mL at 0800 h to 50.9 (13.4) ng/mL at 1800 h (difference log periostin −0.05, P ≤ 0.001) and 50.5 (13.0) ng/mL at 0800 h to 46.2 (11.5) ng/mL at 1800 h (difference log periostin −0.08, P ≤ 0.001) respectively.ConclusionsPeriostin values are higher in the morning compared with the afternoon in asthmatic and non-asthmatic adults. The small magnitude of the variation in serum periostin levels suggests that the time of day in which the serum periostin measurements are made is unlikely to influence treatment decisions if a specific serum periostin level is used to predict treatment responsiveness. Trial registration Australia New Zealand Trials Registry (ACTRN12614000072617)Electronic supplementary materialThe online version of this article (doi:10.1186/s13223-017-0182-0) contains supplementary material, which is available to authorized users.

Although separation in paracetamol dosing is likely to be achieved with a liberal vs. restricted paracetamol regime, ibuprofen is the preferred comparator treatment in the proposed RCT of paracetamol use and risk of asthma in childhood.