42 CFR §493.1264

1. (a)The laboratory must have available a reference collection of slides or photographs and, if available, gross specimens for identification of parasites and use these references in the laboratory for appropriate comparison with diagnostic specimens.
2. (b)The laboratory must calibrate and use the calibrated ocular micrometer for determining the size of ova and parasites, if size is a critical parameter.
3. (c)Each month of use, the laboratory must check permanent stains using a fecal sample control material that will demonstrate staining characteristics.
4. (d)The laboratory must document all control procedures performed, as specified in this section.