The confusion between asthma and COPD seems to be bigger than expected. Unfortunately, some patients are being told they have asthma when in fact they have COPD. Moreover, sometimes it’s not easy to point out to a difference. This also leads to inappropriate therapies for the right patient. Looking for clues may be difficult and some researchers are finding results.
Systemic Biomarkers of inflammation in COPD: under scope
Don D. Sin and colleagues recently published their results on the effects of a combined therapy in COPD on systemic biomarkers of inflammation (Am J Respir Crit Care Med 2008;177:1207-14 - Editorial: 1177-78). Many clinicians expect to provide relief targeting the inflammatory component of COPD. This may be the result of a misunderstanding of symptoms but it may also be linked to the relevance of exacerbations (for patients and physicians).
The details of the biology of COPD is still under research. Particularly, the inflammatory signal is mostly seen during exacerbations. In the meantime we, patients and physicians, are forgetting the stable presentation and probably the masquerading of this disease.
Inflammation as exacerbation or viceversa
COPD is not a disease of exacerbations only. COPD is a disease that exists when exacerbations are in their way. Not treating the stable component (chronic obstruction) will lead to an increase in the incidence of exacerbations.
However, the question is: what are the inflammatory markers of the disease if not the exacerbations?
Indicators of active disease
As it is indicated by Sin and cols. inflammation has its role in the progression of the disease. Inflammation also results in the systemic manifestations associated to the disease like muscle weakness, arrythmias, myocardial infarction, strokes, and sudden deaths (among several others). Of course, neither physicians nor patients want to wait for those indicators to be sure that there’s inflammtion to treat. We rely on the occurrence of exacerbations and, addressed by this, try to treat them although they don’t occur.
Chemical naturally occurring compounds
Some chemical substances have been associated to the development or progression of the inflammation in COPD. C-reactive protein, IL-6 and surfactant protein D (SP-D) are being considered markers of some good quality to assess the intensity of inflammation in the COPD patient. A measurement of this natural occuring substances may help support the occurrence of inflammation. Dr. Sin found that our prefered Trojan Horse for asthma have no impact on some of these components (CRP or IL-6) in patients with stable COPD. They did find a ralation with SP-D which synthesis is predominantly found in the lungs (assessed by mRNA expression).
What is interesting from the published trial is that deficits in SP-D in mice results in development of emphysema (one on the manifestations of COPD). Then, why are we trying to reduce their elevated levels in COPD? Shouldn’t we try to encourage their increase?
Many questions may arise from the published results. Maybe SP-D is not the best biomarker in COPD neither (at least to follow therapy response). COPD has been getting increased attention of pulmonologists and other especialists. Thanks to this a new chapter in the medicine’s history is being written.
Diagnosis COPD based on exacerbations only?
The true is that we shouldn’t base COPD diagnosis on exacerbations. COPD diagnosis is based on the clinical record and a confirmatory spirometry. The biomarker of inflammation is still around by and it isn’t the clinical issue of exacerbations.
Asthma field is also hiding the “real” biomarker (an this disease has received attention). The point is that we know that the insult at the lungs develop a response and while in asthma the main response toward the end is inflammation in COPD it is chronic constriction.
Let’s talk and then treat
Patients need to talk about the differences between COPD and asthma to receive from them a good support in the diagnosis process. The patient may be the real biomarker (metaphorically), then we could first evaluate them and measure their whole response.