A STATISTICAL-ANALYSIS OF MODIFIED CLINICAL TECHNIQUE VISION SCREENING OF PRESCHOOLERS BY OPTOMETRY STUDENTS

Fourth year optometry students screened 745 preschoolers using a sligh tly altered Modified Clinical Technique (MCT) under the supervision of a faculty doctor. Children who failed the MCT were randomly selected and then matched by age, sex, and ethnic origin to children who had pa ssed the screening battery. The 61 screening failures and 45 matched c ontrols were later given full eye examinations with cycloplegia by Uni versity of Alabama at Birmingham faculty doctors who were unaware of t he screening results. The positive predictive value (PPV) (0.52) and n egative predictive value (NPV) (0.78) of the MCT were calculated direc tly from the 2x2 contingency table crossing screening results and a st andard diagnosis. Sensitivity [0.50, k(1,0)=0.29], specificity [0.79, k(0,0)=0.30], efficiency [0.70, k(0.5,0)=0.29] of the MCT, and the pre valence (0.30) of children failing the standard diagnosis were estimat ed using statistics appropriate to the prospective sampling design. Th e reproducibility of the diagnosis, estimated by analyzing multiple, i ndependent diagnoses of each study child by seven doctors was moderate (kappa(D) 0.58). Statistics summarizing the agreement between the MCT and the diagnosis by the individual study doctor are similar to those obtained with comparison to the standard diagnosis. The characteristi cs of the MCT may be generalized only to similar populations that are screened by clinicians with similar experience, using the same tests.