CXCL12 and idiopathic pulmonary fibrosis: Additionally, in IPF never-smokers the directly proportional relationship in blood of CXCL12 levels and fibrocyte percent prevalence was demonstrated (Spearman’s ρ = -0.86, 99% CI −0.677 to 1.0; p = 0.01, Fig. 5B) with a weaker, similar relationship observed in the small number of IPF smokers (data not shown).