Semen Analysis and Semen Evaluation
Core concepts
The semen analysis is a descriptive, probabilistic test, not a fertility diagnosis. Master the WHO-style workflow: abstinence interval (typically 2–7 days), collection completeness, liquefaction within about 60 minutes, and measurement of volume, pH, concentration, total sperm number, motility grades (progressive, non-progressive, immotile), vitality (eosin-nigrosin or hypo-osmotic swelling), morphology (strict or Tygerberg criteria), and round-cell count with differentiation. Understand the difference between concentration (per mL) and total sperm count (concentration × volume), and between percentages and absolute numbers of progressively motile or morphologically normal sperm.
Traps
Questions exploit unit confusion (millions/mL vs millions/ejaculate), grading drift (calling non-progressive motility "progressive"), and the fact that a single normal result does not exclude male factor infertility-biological variability demands repeat testing, often after 2–4 weeks. Vitality should not exceed 100% minus the immotile fraction; a vitality result higher than that signals a counting error. Morphology is observer-dependent, so strict criteria and internal QC matter. Dilution errors and counting-chamber loading artifacts (overfilling, drying) are classic distractors.
Worked example / rule of thumb
If volume = 3.0 mL and concentration = 20 million/mL, total sperm number = 60 million. If 40% are progressively motile, absolute progressively motile count = 0.40 × 60 million = 24 million. Rule of thumb: always convert percentages to absolute counts before interpreting clinical significance, and flag any result where vitality plus immotility exceeds 100% as a technical error requiring re-analysis.