What's your system: WD or EDXRF?

Yes, logically it may be possible for W L-X-ray lines due to Coster-Kronig transitions. There can be change in La-Lb intensity ratios if W is chemically bound. You can cross -check with a pure W foil ...or better still, a thin W-film (few micro-gm/cm2) would give you the pristine ratio of W La-Lb line (i.e. in its pure form)....Of course you can find the relative intensities from literature but it's better to compare in your instrument.

Thanks for your answer, do you some literature on that?

Sorry, I forgot to tell you that our system is an EDX.

Any standard reference: " Handbook of X-ray spectrometry" by Van Grieken & Markowicz..etc. You can look up the NIST web-site too for X-ray fundamental parameters...or X-ray "Fundamental parameters" library in google.