The invention relates to a method of diagnosing or screening for 27-hydroxylase (CYP27A1) deficiency in an animal comprising: determining in a biological sample the intensity signal by mass analysis of at least a bile alcohol glucuronide and a C24- or C27-bile acid or a conjugate thereof, comparing the intensity signals to a control sample or control value, and determining 27-hydroxylase (CYP27A1) deficiency based on said comparison.

The invention relates to a method of diagnosing or screening for 27-hydroxylase (CYP27A1) deficiency in an animal comprising: determining in a biological sample the intensity signal by mass analysis of at least a bile alcohol glucuronide and a C24- or C27-bile acid or a conjugate thereof, comparing the intensity signals to a control sample or control value, and determining 27-hydroxylase (CYP27A1) deficiency based on said comparison.

The present invention refers to the field of food safety and environmental control. In particular, it refers to a method for the detection of chemical contaminants based on cytochrome P450 enzymes, to a kit to carry out said method and to its use.