Medical Insurance premium deduction

My wife has a employer-sponsored insurance plan and I am listed as a spouse on that plan. We are filing as Married, Filing Jointly.

Her bi-weekly pay stubs show that her employer pays X amount in medical insurance premiums and my wife pays an additional amount that is roughly 20% of the X amount that the employer pays. Of that 20%, about two thirds is listed as pre-tax cost per a print out from the employer's HR Dept.

IRS Pub 502 states you can deduct medical insurance premiums and a half a page later says you cannot unless they are listed on the W-2.

There is no indication of insurance premiums paid anywhere on her W-2.

What am I missing here?

Thanks for your help.