Objective: To evaluate a novel expression of sperm morphological parameters, the sperm deformity index, as a predictor of fertilization in vitro.
Design: Prospective blind clinical trial.
Setting: Academic tertiary referral center.
Intervention(s): Detailed sperm morphological assessment applying strict morphological criteria and a multiple entry technique for an unselected male population undergoing IVF. The sperm deformity index, defined as the average number of deformities per sperm assessed, was calculated.
Patient(s): One hundred fifty-eight patients undergoing IVF treatment. Females with conditions negatively influencing fertilization were excluded.
Main outcome measure(s): Fertilization rates and pregnancy.
Result(s): Seventy-three percent of patients achieved fertilization. Patients achieving fertilization had a significantly higher median proportion of normal forms and a significantly lower median sperm deformity index than the nonfertilizers. The receiver operator characteristic (ROC) curves identified cutoff points that maximized the sum of sensitivity and specificity at sperm deformity index 1.6 and normal forms 4%. The sperm deformity index had a greater sensitivity (96%), specificity (72%), positive predictive value (90%), and negative predictive value (86%) than the proportion of normal sperm morphology (87%, 69%, 89%, 66%, respectively) at the optimal cutoff points. The area under the ROC curve was greater for the sperm deformity index (0.875) than for the proportion of normal sperm morphology (0.622). Achieving pregnancy did not correlated with sperm morphology.
Conclusion(s): The sperm deformity index is a more reliable predictor of the outcome of fertilization in vitro than the proportion of normal sperm morphology and can assist to identify patients who require techniques such as intracytoplasmic sperm injection.