Variability in objective and subjective measures affects baseline values in studies of patients with COPD.

Anderson WH, Ha JW, Couper DJ, O'Neal WK, Barr RG, Bleecker ER, Carretta EE, Cooper CB, Doerschuk CM, Drummond MB, Han MK, Hansel NN, Kim V, Kleerup EC, Martinez FJ, Rennard SI, Tashkin D, Woodruff PG, Paine R, Curtis JL, Kanner RE