Serum periostin levels do not need to be adjusted to take account of a patient’s age, sex, or common comorbidities [8], although periostin levels may be lower in smokers [8], in those with elevated BMI [8], and those with pre-extant osteoarthritis [9], and may be raised in a number of cancers [10]. The gene discussed is POSTN; the disease is osteoarthritis.