Increased Reid index is classically associated with?
**Core Concept**
The Reid index is a histopathological parameter used to assess the thickness of the mucous glands in the respiratory tract. It is calculated by dividing the thickness of the mucous gland layer by the distance between the basement membrane and the cartilage in the trachea. An increased Reid index suggests an abnormal proliferation of mucous glands, which can be a hallmark of certain respiratory conditions.
**Why the Correct Answer is Right**
An increased Reid index is classically associated with chronic bronchitis, a type of chronic obstructive pulmonary disease (COPD). This is because chronic bronchitis is characterized by an abnormal increase in the number and size of mucous glands in the airways, leading to excessive mucus production and chronic inflammation. The increased mucous gland thickness is thought to be a response to chronic irritation and inflammation in the airways, which can be caused by smoking, air pollution, or other environmental factors.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not directly related to the Reid index or chronic bronchitis. While asthma is a respiratory condition, it is characterized by airway inflammation and hyperresponsiveness, rather than an increase in mucous gland thickness.
* **Option B:** This option is not a specific condition associated with an increased Reid index. While lung cancer can cause changes in the airways, it is not typically characterized by an increase in mucous gland thickness.
* **Option C:** This option is not a condition that is directly associated with an increased Reid index. While chronic cough is a symptom of chronic bronchitis, it is not a specific diagnosis that is characterized by an increase in mucous gland thickness.
**Clinical Pearl / High-Yield Fact**
The Reid index is a useful diagnostic tool in the evaluation of patients with chronic respiratory symptoms. A high Reid index can help differentiate chronic bronchitis from other respiratory conditions, such as asthma or lung cancer.
**Correct Answer: C. Chronic bronchitis.**