Table 2.

Description of analgesic index scores.

Score	Description	Calculation
Difference	Post-drug values subtracted from pre-drug values	= b − a
Percent Change	Difference scores divided by pre-drug values × 100	$=\frac{b-a}{b}\times 100$
Ratio	Post-drug values divided by pre-drug values	= b/a
Residualized	Covarying out pre-drug values from post-drug values	Regression of post-drug values on pre-drug values

Abbreviations: a, pre-drug values; b, post-drug values; c, cut off value