Comparison of different scoring systems for immunohistochemical staining.

AIM To carry out an objective assessment of two systems of scoring immunohistochemical staining, evaluating interobserver and intraobserver error. METHODS 92 cervical tumours underwent immunohistochemical staining for p53 and epidermal growth factor receptor. Staining was assessed using two methods: a standard 4 point scale and a descriptive method, performed by three observers. Interobserver and intraobserver error were assessed for both scoring methods. RESULTS In terms of interobserver error between three observers, no difference was found between a simple 4 point scale method of evaluation and the use of a highly circumscribed method. In all evaluations, interobserver error was scored as moderate (kappa w 0.48-0.49). However, evaluation of immunohistochemical staining by a panel of observers led to a marked improvement in the interobserver error scores (kappa w 0.63). CONCLUSIONS There should be standardisation of immunohistochemical staining and scoring methods. More attention should be paid to measurement of interobserver and intraobserver error in studies. Use of a panel of tissue control slides and consensus scoring by several observers can lead to improvement in reproducibility.