1. C4d Recomendations
C4d staining should be done on all diagnostic renal transplant biopsies.

2. Criteria for C4d Positivity
1. Cryostat section, Monoclonal Ab, immunofluorescence.
Widespread, strong, linear, circumferential,
peritubular capillary staining in either cortex or medulla
Excluding scarred or necrotic areas
Concurrent positive control (essential, if neg being
reported)   
Reports should include the % of area of positive PTC and intensity.

3. Criteria for C4d Positivity
2. Paraffin, Polyclonal Ab, immunohistochemistry
Same as frozen tissue, but
strong staining not required*
*The type of pretreatment influences the intensity. GBM/mesangial staining in the sample cannot be used as a positive control, but membranous GN is satisfactory.