Reliability of the sperm chromatin dispersion assay to evaluate sperm deoxyribonucleic acid damage in men with infertility

Abstract

Objective: To investigate the intraindividual agreement of the sperm chromatin dispersion (SCD) assay results to assess sperm DNA fragmentation (SDF) in men with infertility.

Design: Diagnostic test reliability study.

Setting: Andrology laboratories.

Patient(s): A total of 219 men with infertility.

Intervention(s): Sperm DNA fragmentation assessment in two ejaculates of the same subjects within a 3-month interval, using the SCD assay performed and analyzed by the same observers under similar testing conditions.

Main outcome measure(s): Cohen's κ statistics to assess the degree of agreement between the pairs of results after converting the nominal SCD values into categorical data, that is, normal (<20%), intermediate (21%-29%), and high (≥30%) SDF rates. We also assessed the pairs of results using reliability measures for numerical variables (intraclass correlation coefficient for consistency using the two-way mixed-effects model and Bland-Altman plots).

Result(s): The degree of agreement in classifying patients according to normal and pathological SDF classes was overall substantial (κ = 0.632; 95% confidence interval [CI], 0.546-0.718). A total of 76.7% of individuals were classified under the same class using paired ejaculates. The agreement rate was highest (approximately 80%) in ejaculates initially classified as either normal or high and lowest (approximately 60%) among those with intermediate SDF levels. The frequency of intermediate SDF ejaculates downgraded to normal or upgrade to high SDF classes in the second test was similar (approximately 20%). The intraclass correlation coefficient was 0.856 (95% CI, 0.812-0.887), and the mean difference between the pairs of observations was 0.80% (95% CI, -0.72 to 2.23), indicating no systematic difference between paired observations.

Conclusion(s): Our study indicates a substantial intraindividual agreement of paired SCD assay results to classify men with infertility into three SDF categories: normal, intermediate, and high. The reliability of the SCD assay was adequate and exceeded 0.80 using two ejaculates analyzed within a 3-month interval under similar conditions. Although this evidence overall supports a single SCD test for patient classification using predefined SDF thresholds, particularly when the first test shows normal or high SDF levels, one in four men will have discordant values in paired ejaculates. Clinicians should be judicious when using SDF test results in decision-making.

Keywords: Semen analysis; agreement study; male infertility; reliability; sperm DNA fragmentation.