I suspected my data was non-linear so I ran PROC GAM to visualize my age variable relative to my binomial outcome. I realize adding one spline knot at age 51.5 was very appropriate. I created the linear piecewise spline using a "relative reference" coding scheme:

if age<=51.5 then age515=0;

else age515=age-51.5;

Next I ran a log binomial regressionPROC GENMOD; dist=bin, link=log) as my outcome variable is very prevalence (>60%). I have the outputs that give me the prevalence ratios for the first regression line up to age <=51.5; how do I get the prevalence ratios for the second regression line >51.5? I have one class variable (four levels) and one continuous variable

From the output:

Analysis Of Maximum Likelihood Parameter Estimates

Parameter Beta

Intercept -2.3315

Age (contin) 0.0328

Var (level 4) 0.6515

Var (level 2) 0.6509

Var (level 3) 0.6515

Var (level 1) 0.0000

Thanks