### Description

The Global Initiative for Asthma (GINA) report has proposed a classification schema for asthma severity. This can help in formulating the management plan for the individual patient.

Classification:

(1) intermittent vs persistent

(2) if persistent: mild, moderate or severe

 Severity Class Symptoms Exacerbations Nighttime Asthma Symptoms PEF or FEV1 intermittent < 1 time per week brief (from a few hours to a few days); asymptomatic between exacerbations < 2 times per month >= 80% of predicted; variability < 20% mild persistent >= 1 time per week but < 1 time per day may affect activity and sleep > 2 times per month >= 80% of predicted; variability 20-30% moderate persistent daily; daily use of inhaled short-acting beta-2 agonist affect activity and sleep > 1 time per week > 60% to < 80% of predicted; variability > 30% severe persistent continuous; physical activities limited frequent frequent <= 60% of predicted; variability > 30%

where:

• PEF = peak expiratory flow

Limitations:

• No single test or measurement can accurately classify the level of asthma severity.

• Criteria for defining disease severity are based on symptoms and changes in pulmonary function before initiation of any therapy.

• With exacerbations the severity of disease can change abruptly and dramatically.

Equations for Predicting PEF from Nunn (1989)

Peak expiratory flow for men:

LN(PEF in L/min) =

= (0.544 * LN(age in years)) - (0.0151 * (age in years)) - (74.7 / (height in cm)) + 5.48

Peak expiratory flow for women:

LN(PEF in L/min) =

= (0.376 * LN(age in years)) - (0.0120 * (age in years)) - (58.8 / (height in cm)) + 5.63

Equations for FEV(1) from Crapo (1981)

predicted FEV(1) in liters for males =

= ((0.0414 * (height in cm)) + ((-0.0244) * (age in years)) - 2.190

predicted FEV(1) in liters females =

= ((0.0342 * (height in cm)) + ((-0.0255) * (age in years)) - 1.578