declare @value decimal(10,2)
set @value = (select 
CASE WHEN %CH003% = 0 THEN 0 
WHEN {AGE,YEAR} > 130.0 THEN 0 
WHEN {AGE,YEAR} < 18.0 THEN ((0.41 * {HEIGHT}) / %CH003%) 
WHEN {SEX} = "M" AND %CH003% <= 0.9 THEN ((141 * (POWER((%CH003% / 0.9), -0.411))) * POWER(0.993, {AGE,YEAR})) 
WHEN {SEX} = "M" AND %CH003% > 0.9 THEN ((141 * (POWER((%CH003% / 0.9), -1.209))) * POWER(0.993, {AGE,YEAR})) 
WHEN {SEX} = "F" AND %CH003% <= 0.7 THEN ((144 * (POWER((%CH003% / 0.7), -0.329))) * POWER(0.993, {AGE,YEAR})) 
WHEN {SEX} = "F" AND %CH003% > 0.7 THEN ((144 * (POWER((%CH003% / 0.7), -1.209))) * POWER(0.993, {AGE,YEAR})) ELSE 0 END)

SELECT CASE WHEN @value > 90.0 THEN "Stage G1"      
WHEN @value >= 60.00 AND @value <= 89.99 THEN "Stage G2"      
WHEN @value >= 45.00 AND @value <= 59.99 THEN "Stage G3a"      
WHEN @value >= 30.00 AND @value <= 44.99 THEN "Stage G3b"      
WHEN @value >= 15.00 AND @value <= 29.99 THEN "Stage G4"      
WHEN @value <  15.00 THEN "Stage G5"      
ELSE "N/A" END