I just had a look for you this dinner time in the Cessna 152 manual and to be honest I cannot find a reference to checking it.
I take it you have one that you suspect is out, how far is it?
I would be tempted to say not to check it from the spinner but from a point on the forward fuselage out to a point on the wing skin, and not the tip, the reason being the engine may well be mounted off slightly to one side and possibly down for the thrust line etc...........
Wing tips can be all over the place, so try to do it to the corner of a skin or a rivet etc on both wings and fuselage sides. also try doing it from the vertical fin mounts forward as they will tend to be set points as a second point of reference......
If I find some more data I will post it for you.......