<p>a) A substantial amount of variation in the average [SP-D] in the serum/plasma of healthy control population exists between studies using the same or different ELISA configurations. Three configurations (Yamasa <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111466#pone.0111466-Greene1" target="_blank">[12]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111466#pone.0111466-Greene2" target="_blank">[13]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111466#pone.0111466-Nagae1" target="_blank">[17]</a>–<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111466#pone.0111466-Kuwano1" target="_blank">[19]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111466#pone.0111466-Lin1" target="_blank">[21]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111466#pone.0111466-Ilumets1" target="_blank">[25]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111466#pone.0111466-Mutti1" target="_blank">[28]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111466#pone.0111466-Krane1" target="_blank">[38]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111466#pone.0111466-Takahashi2" target="_blank">[43]</a>–<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111466#pone.0111466-Yanaba1" target="_blank">[45]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111466#pone.0111466-Janssen1" target="_blank">[49]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111466#pone.0111466-Koopmans1" target="_blank">[50]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111466#pone.0111466-Kawasaki1" target="_blank">[59]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111466#pone.0111466-AlSalmi1" target="_blank">[61]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111466#pone.0111466-Haddam1" target="_blank">[77]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111466#pone.0111466-Ihn1" target="_blank">[84]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111466#pone.0111466-Stapleton1" target="_blank">[89]</a>, BioVendor <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111466#pone.0111466-Glas1" target="_blank">[14]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111466#pone.0111466-Lomas1" target="_blank">[31]</a>–<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111466#pone.0111466-ElDeek1" target="_blank">[36]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111466#pone.0111466-Hant1" target="_blank">[46]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111466#pone.0111466-Vizcaya1" target="_blank">[52]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111466#pone.0111466-Bejvl1" target="_blank">[56]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111466#pone.0111466-Wutzler1" target="_blank">[64]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111466#pone.0111466-Engstrom1" target="_blank">[65]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111466#pone.0111466-Wang1" target="_blank">[72]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111466#pone.0111466-Shiels1" target="_blank">[75]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111466#pone.0111466-Aul1" target="_blank">[76]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111466#pone.0111466-Gil1" target="_blank">[79]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111466#pone.0111466-FernandezLuna1" target="_blank">[80]</a>, and Holmskov et al. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111466#pone.0111466-Hohwy1" target="_blank">[3]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111466#pone.0111466-Olesen1" target="_blank">[39]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111466#pone.0111466-Hoegh1" target="_blank">[53]</a>–<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111466#pone.0111466-Wu1" target="_blank">[55]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111466#pone.0111466-LethLarsen1" target="_blank">[58]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111466#pone.0111466-Heidinger1" target="_blank">[62]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111466#pone.0111466-Sorensen1" target="_blank">[66]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111466#pone.0111466-Zhao1" target="_blank">[69]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111466#pone.0111466-Hoffmann1" target="_blank">[70]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111466#pone.0111466-Gravholt1" target="_blank">[78]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111466#pone.0111466-Nybo1" target="_blank">[85]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111466#pone.0111466-Hoegh3" target="_blank">[86]</a>) were compared. b) The range of healthy control [SP-D] greatly varied from study to study. Values shown are either median and interquartile range (IQR), median and 95% confidence interval (95%), or mean and standard deviation (SD). c) The calculated fold increase from the average healthy [SP-D] and average [SP-D] during IPF <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111466#pone.0111466-Greene1" target="_blank">[12]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111466#pone.0111466-Honda1" target="_blank">[16]</a>–<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111466#pone.0111466-Kuwano1" target="_blank">[19]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111466#pone.0111466-Lin1" target="_blank">[21]</a>, CF <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111466#pone.0111466-Sims1" target="_blank">[15]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111466#pone.0111466-Krane1" target="_blank">[38]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111466#pone.0111466-Olesen1" target="_blank">[39]</a>, cigarette smoking <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111466#pone.0111466-Mutti1" target="_blank">[28]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111466#pone.0111466-Lomas1" target="_blank">[31]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111466#pone.0111466-Wang1" target="_blank">[72]</a>–<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111466#pone.0111466-Shiels1" target="_blank">[75]</a>, or sclerosis <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111466#pone.0111466-Elhaj1" target="_blank">[42]</a>–<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111466#pone.0111466-Asano1" target="_blank">[44]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111466#pone.0111466-Hant1" target="_blank">[46]</a> was different between publications. An asterisk (*) denotes p≤0.001 by one-way ANOVA with Tukey's multiple comparison test.</p
