Pus, deoxyribonucleic acid, and sputum viscosity.

On 100 sputum specimens selected from patients suffering from chronic bronchitis, bronchiectasis, 
asthma, and cystic fibrosis total deoxyribonucleic acid (DNA) content has been 
related to macroscopic type, to total dry weight yield, and to 
the apparent viscosity of the secretion at 1350 s-1: since DNA 
may be present, either as fibres or within cells, in one-third 
of the specimens the contribution of each form to the apparent 
viscosity was assessed. The effect on sputum viscosity of the addition 
of DNA in vitro has also been studied. Whereas between mucoid, 
mucopurulent, and purulent macroscopic types a significant difference in total DNA 
and dry weight yield has been found, viscosity was not significantly 
correlated with purulence. Similarly, the concentration of either cells or fibres 
correlated significantly with total DNA but not with viscosity. The in 
vitro addition of DNA to sputum caused a significant increase in 
its viscosity, and reasons for the differences between the iv vivo 
and in vitro effect are discussed. Certain constituents of purulent sputum 
tend to increase viscosity and others to reduce it, and the 
influence of these varies in the several diseases studied. 