Performance Evaluator

The performance of the CMD system primarily depends on the classification efficiency of the classifier. The performance evaluator assesses the classification efficiency using four evaluation measures presented in Equations (2) to (5). The four measures, namely, Precision, Sensitivity, Specificity, and Accuracy, differ in their criterion of evaluation. Precision evaluates the agreement of the class label with the positive labels predicted by the classifier. Sensitivity is used to evaluate the effectiveness of a classifier to identify positive labels, whereas Specificity evaluates how effectively a classifier identifies negative labels. Accuracy evaluates the overall classification efficiency of the classifier. Table 2 presents the confusion matrix. True positives (tp) refer to those samples that are positive and correctly diagnosed as positive (patient has urticaria and is allergic). Likewise, true negatives (tn) refer to those samples that are negative and correctly diagnosed as negative (patient does not have urticaria). False positives (fp) are those samples that are diagnosed as positive by the system/clinician but are actually negative as per the expert’s diagnosis (gold standard). False negatives (fn) are those samples that are affected with urticaria but diagnosed as negative by the system/clinician.

Confusion Matrix

Intradermal skin test data were collected from 778 patients who visited the Good Samaritan Lab and Allergy Centre, Chennai, Tamilnadu, India, between 1 March and 20 June 2013. The patients were referred by ENT surgeons and general physicians because of skin diseases, itching, or other plausible allergic symptoms. A total of 365 males and 413 females, of all age groups, were included in the study.

After analyzing the medical history of a patient, the allergist determines whether skin testing is appropriate for the patient. The allergist also determines the list of selected allergens to be tested. Allergen extracts, negative controls (saline), and positive controls (histamine) were used for performing the skin tests. The upper half of the volar surface of the forearm was selected for the test. It was cleansed with alcohol and a pen is used to label the area in a grid-like pattern to depict where the extract (allergen) is to be applied. About 0.01 mL of the allergen is injected into the epidermis using a sterile, disposable, plastic 1-mL tuberculin syringe. Patients were asked to stop taking antihistamines and anti-allergic drugs and medications. Table 3 lists the medication to be avoided before allergy testing.

Medication to Be Avoided Before Allergy Testing

Consecutive observations, on an hourly basis, were taken. A positive reaction is depicted by a wheal and a flare reaction.^8,23 A negative response to a skin test usually indicates that the patient is not sensitive to that allergen. For patients who reported a delayed response to the test, the reactions were incorporated in the results.