CRP and chronic obstructive pulmonary disease: Other studies including C-reactive protein (CRP) and pro-calcitonin testing [3,4] have tested pro-calcitonin levels in acute exacerbation chronic obstructive pulmonary disease (AECOPD) patients for a possible viral etiology and proposed that the elevation of pro-calcitonin or CRP in the patient’s blood sample has a strong association with a bacterial source.