It is used to assess respiratory function and is measured using a spirometer. Forced Vital Capacity (FVC) refers to the maximum volume of air that can be forcefully exhaled from the lungs after a full inhalation. This value can be expressed in liters or as a percentage.

It is employed to assess respiratory functions and is measured using a spirometer. Forced Expiratory Volume in the first second (FEV₁) represents the volume of air that can be forcefully exhaled within the first second of a maximal exhalation. This parameter can be expressed either in liters or as a percentage.

It is employed to assess respiratory function and is measured with a spirometer. The value is obtained by dividing FEV₁ by FVC, and the result is expressed as a percentage.

Carbon monoxide diffusion capacity (DLCO) is the measurement of the passage of carbon monoxide gas in inspired air into the lung capillary blood. Diffusion test is performed in the pulmonary function test laboratory.

The Gender-Age-Physiology (GAP) index is a multidimensional assessment index developed and validated to predict mortality in ILD. The ILD-GAP index is divided into stages 0-1, 2-3, 4-5, and >5, which predict the risk of death in the 1st, 2nd, and 3rd years. The GAP index will be calculated based on gender (0-1 points), age (0-2 points), %FVC (0-2 points), and %DLCO (0-3 points). It is classified into Stage I (0-3 points), Stage II (4-5 points), and Stage III (6-8 points), with prognosis worsening as it progresses from Stage I to Stage III.

The Modified Medical Research Council (mMRC) Dyspnea Scale assesses the sensation of breathlessness as perceived by the individual. The severity of dyspnea is scored on a scale ranging from 0 to 4, where 0 indicates no perception of dyspnea and 4 represents severe breathlessness.

A manual hydraulic dynamometer will be used for the hand grip strength test, taking into account the recommendations of the American Association of Occupational Therapists (AAOT). During the test, measurements will be taken while the patient is seated with back support, shoulder in adduction and neutral position, elbow at 90° flexion, and forearm in neutral position.

he fatigue levels of individuals will be evaluated using the Fatigue Severity Scale. This scale comprises nine items rated on a 7-point Likert scale, reflecting the individual's perception of fatigue, which may indicate the need for medical intervention. The total score is 63. Higher scores indicate more severe fatigue.

The feeling of breathlessness experienced during daily living activities was assessed using the London Chest Daily Activities of Living Scale (LCADL). The scale consists of a total of 15 items divided into four sections: personal care (4 items), housework (6 items), physical activity (2 items), and leisure activities (3 items). Each item is scored on a scale of 0-5. The total score for the scale is 75. A high score indicates an increased perception of shortness of breath during daily living activities.

The St. George's Respiratory Questionnaire is designed to assess health-related quality of life in individuals with respiratory conditions. It provides four separate scores: Symptoms, Activity, Impacts, and an overall Total score. The scale ranges from 0 to 100, where 0 represents no impairment in quality of life and 100 indicates the most severe impairment.