Genetic counseling of asymptomatic carriers in a primary care setting. The effectiveness of screening and counseling for beta-thalassemia trait.

In a prospective, controlled, stratified, experimental effectiveness study of screening and counseling, 25 000 consecutive adults were screened for thalassemia trait. Eight hundred forty-three adults had a mean corpuscular volume less than 77 fL; 192 (22% of those with microcytosis) had hemoglobin A2 greater than 3.5%, proving beta-thalassemia trait. Video-program, neutral-educational, and patient-centered counseling methods produced equal levels of learning, retention, psychologic impact, and effects on life adjustment immediately and at 2 and 10 months after counseling. Ninety-nine percent of the patients told other persons about the counseling, and 43% had 106 others screened. Factors related to having someone else screened included plans to have children (p less than 0.002), being younger (p less than 0.0025), better education (p less than 0.05), and having high knowledge of thalassemia (p = 0.05). For maximum effectiveness, screening and counseling programs should focus on patients for whom a positive result has high significance.