[Histonet] CD68 counts

[Edwards, R.E.]

I am attempting to accurately assess the number of CD 68 positive cells (hopefully macrophages) in biopsies,  they have been GMA processed, ABC staining, with AEC visualisation;  no problem with a nucleated cell with positive cell  membrane, but  they  are  in  the minority, so  the  question how  does one judge the cut-off point that makes a positive cell  into a negative cell  if you catch my drift??. I am quite experienced at counting cells but feel that obtaining reliable, consistent results from this material is quite challenging.
               All ideas/thoughts gratefully received

                         Cheers
                                Richard Edwards
                                  University of Leicester
                                            U.K.