Accuracy of cytological evaluation of sputum in differentiation of asthma-chronic obstructive pulmonary disease

Background
Biomarkers of airway inflammation are valuable in the assessment of phenotypes of obstructive lung diseases. The therapeutic relevance of sputum cytology in chronic obstructive pulmonary disease (COPD), asthma, and asthma-COPD overlap (ACO) is still ambiguous. This research sought to assess the utility of sputum cell count in distinguishing between asthma, COPD, and ACO.


Patients and methods
A total of 66 patients were recruited and categorized based on their diagnosis into three groups: asthma, COPD, and ACO group, 22 patients each. After thorough history taking and clinical evaluation, collection of sputum samples was done and sent for cytological examination by a consultant pathologist.


Results

Asthma participants had a significantly lower mean age than those with COPD. The COPD group had significantly lower FEV1%, FVC%, and forced expiratory volume in 1 second/forced vital capacity (FEV1/FVC) ratio than those with ACO or asthma. The Eosinophilic count was significantly elevated among cases of asthma (6.5 vs. 2;
P
< 0.001) and ACO (5 vs. 2;
P
< 0.001) compared with COPD cases. There was no significant difference as regard neutrophil count in ACO and COPD however, both had significantly higher counts than asthmatic patients; ACO versus asthma (87 vs. 68.5;
P
< 0.001), COPD versus asthma (87 vs. 68.5;
P
< 0.001). COPD cases had a significantly elevated count of lymphocytes in comparison to asthma (2 vs. 1;
P
= 0.02) and ACO (2 vs. 1;
P
< 0.001). Asthma group had significantly higher macrophages count than COPD (11 vs. 2.5;
P
< 0.001) and ACO (11 vs. 6;
P
< 0.001).



Conclusion
Sputum cytology is a simple noninvasive method useful in differentiation between asthma, COPD, and ACO. Future research are still warranted to confirm such findings.