GAPDH and chronic obstructive pulmonary disease: Using real-time quantitative PCR analyses, there was a significant increase in the expression of CLCA1 mRNA per 10,000 copies of GAPDH mRNA in sputum cells from COPD patients (579 ± 179 copies, p = 0.02) compared to cells from non-smokers (73 ± 26 copies) (Figure 1).