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.