Quantification of Immunohistochemistry Using an Image Analyser: Correlation with Hormone Concentrations in Pituitary Adenomas

The usefulness of immunohistochemistry is usually confined to qualitative analysis. Quantitative evaluation is not performed. At best, the number of immunopositive cells and the immunointensities are recorded as several grades, to which a strict categorization may be applied by individual examiners, but these categorizations are not standardized. We have attempted to quantify immunohistochemical observations using an image analyser. Sections from rat pituitary adenomas secreting prolactin and growth hormone were immunostained for these hormones with either immunogold silver or avidin-biotinylated peroxidase complex (ABC) methods. The number of immunopositive cells were counted by eye on specimens stained with the ABC method. In sections stained by an immunogold-silver technique, an immunopositive area was measured at several immunointensity ranges, to which certain points were allotted. Immunohistochemical values obtained by summing the products of the immunopositive area and intensity points at each range were correlated with concentrations of hormones in adenoma tissues measured by radioimmunoassay. A high correlation between the immunohistochemical values and hormone concentrations were shown for both prolactin and growth hormone, in contrast to a low correlation between the number of immunopositive cells counted by eye and the hormone concentrations. These findings indicate that the immunohistochemical observations can be quantified using the image analyser to the extent that they can be substituted, albeit roughly, for the hormone concentrations measured biochemically.