Help interpreting test results

[RP56]

I'm a 48yr female, quit smoking 23 yrs ago. I've had shortness of breath on exertion for two months. Pumonologist was concerned about possible pulmonary fibrosis. Test results as follows: HRCT "shows minimal infiltrate/scarring in the anterior segment of the right lower lobe/right lung base," no other abnormality.  PFT showed "minimal obstructive defect," FVC 110, FEV1 103, FEF25-75% 85, VC 110, TLC 87, FRC N2 76, DLCO 70, DLCO/VA 90.  Four years ago, I had a debilitating viral infection & my DLCO was 58%, so it's better now (I had mono eight years ago & it affected my immune system). Pulmonologist very reassuring, said no sign of IPF or other ILD(good!) but also that sob wasn't from lungs (cardiac cause has been ruled out, btw). My FP disagrees.  Can you please explain "scarring/infiltrate" versus pulmonary fibrosis? Is lung scarring common? Can the HRCT tell for certain something is scarring? My FP says it could a virus, walking pneumonia, etc. Is it possible to experience sob on exertion based on these PFT results, and should I have any concern about the HRCT findings? My SP02 halfway through the PFT was 92%.  
Thanks for your help.

[National Jewish]

Your pulmonologist is certainly correct in being concerned about possible pulmonary fibrosis.  Segmental infiltrate/scarring is not a sign of pulmonary fibrosis.  Your otherwise normal high-resolution CT (HRCT) scan along with your normal PFTs are strong evidence that you do not have pulmonary fibrosis.  Ask your pulmonologist about the FP’s comment about walking pneumonia.

Your PFTs do not explain your shortness of breath.  You’ll need more testing to find the problem that is causing your shortness of breath.  An exercise study and lung scan could be helpful.