Have you applied scale to the filament just in case the geometry is off? Might not work but sometimes scale has a weird effect on things.
Object > Apply > Scale.
Thanks for the answer... Doesn't work...
What are your glass-shader settings? Did you set it to 'thin surface'? That will drastically reduce noise in your render. As well i found out, that the direction of the normals of the glass object is important, maybe you just try recalculating or flipping them.
Here's some hints:
1. Thin surface. Use this if your glass is a flat plane (or has 0 thickness). If you model your light bulb here as two layers of polygons and want glass material to be BETWEEN the two surfaces, don't do this. Otherwise if it's a single layer of polygons as glass with air in the middle use thin glass.
2. Allow caustics . Does more correct caustic computation, otherwise pretends the glass is semi transparent to shadows.