Routine 5 μm H&E-stained lung sections were utilized to investigate the capability of histomorphometry for determining pneumonia severity using
a murine influenza model. Lung density was measured using the NIH ImageJ software program and the results for binary digital images were
compared to corresponding results for semiquantitative pneumonia severity scoring. Lung samples from mice exposed (inoculated controls or
IC) or not exposed (non-inoculated controls or NC) to influenza virus were evaluated at 3-, 5-, 7-, 10- and 15-days following exposure. On day
15 the mean density and standard deviation for NC at 25-x were 106 ± 23.6 and for IC 154.9 ± 36.3, and the difference was significant (p ≥
0.05). Using 400-x measurements NC values were 68.1 ± 8.5 and IC 96.8 ± 16.1 and significant. Significant differences were present at either
magnification in the occurrence of “morphometric pneumonia” (defined as density values above the upper 95% confidence interval of controls).
Density measurements @ 25-x were moderately correlation with pneumonia severity scores (correlation coefficient or r=0.55), but measurements
@ 400-x were strongly correlation with scores (r=0.75). The approach provides a simple, rapid, and inexpensive method for the quantification of
pneumonia using free digital software and routine microscopy. It also provides a quantitative method for validation of semiquantitative severity
scoring of pneumonia.