What is preferred for sperm preparation, spermfuge (sperm wash) or centrifuge?

Sperm Preparation: Centrifuge-Based Methods Are Preferred

For sperm preparation in assisted reproduction, density gradient centrifugation is the preferred method over simple sperm wash (centrifuge alone), though the evidence shows no clear superiority of any single technique when comparing clinical pregnancy outcomes. 1

Evidence-Based Recommendation

The most recent WHO guideline (2018) explicitly states: "According to the available evidence, it is not possible to recommend any semen preparation technique over another (swim-up, gradient, wash and centrifugation)." 1 This recommendation is based on:

• A Cochrane systematic review that found no significant difference in pregnancy rates among techniques: swim-up versus gradient (OR = 1.57,95% CI: 0.74–3.32), swim-up versus wash and centrifugation (OR = 0.41,95% CI: 0.41–1.10), or gradient versus wash and centrifugation (OR = 1.76,95% CI: 0.71–5.44) 1

• The overall quality of evidence was graded as low due to clinical heterogeneity, unclear randomization methods, and small sample sizes 1

When to Choose Density Gradient Centrifugation

For couples with unexplained infertility specifically, density gradient centrifugation shows superior outcomes. The most recent relevant RCT (Karamahmutoglu et al., 2014) found significantly higher ongoing pregnancy rates with density gradient centrifugation (SpermGrad) compared to swim-up: 23.4% versus 10.7% (P < 0.05) 1

Technical Advantages of Density Gradient Centrifugation:

• Higher sperm recovery rates compared to swim-up, making it suitable for both normal and abnormal semen samples 1

• More efficient separation from seminal plasma, minimizing bacterial carryover and selecting spermatozoa with reduced DNA damage 2

• Better for oligozoospermia: Swim-up results in lower recovery rates and is only suitable for normozoospermic cases 1

When Swim-Up May Be Considered

Swim-up technique is acceptable only in cases of normozoospermia where sperm concentration and motility are normal 1. However, even in these cases:

• Some studies report comparable or even lower motility with swim-up compared to gradients 1

• The percentage of morphologically normal spermatozoa may not be superior with swim-up 1

Critical Centrifugation Parameters

Centrifugation Time (More Important Than G-Force):

• Shorter centrifugation periods (2 minutes) are superior to longer periods (10 minutes) for minimizing reactive oxygen species (ROS) formation 3

• Prolonged centrifugation significantly increases ROS production regardless of g-force, causing iatrogenic sperm injury through lipid peroxidation 3

Temperature During Centrifugation:

• Room temperature centrifugation is acceptable - an RCT of 671 couples found no differences in sperm parameters or pregnancy rates between controlled (body/testis temperature) and non-controlled (room temperature) centrifugation 1

Common Pitfalls to Avoid

• Avoid prolonged centrifugation times: Keep centrifugation to 2 minutes when possible to minimize ROS-induced damage 3

• Do not use swim-up for oligozoospermia: Recovery rates will be inadequate 1

• Avoid multiple centrifugation steps without density gradient: Simple wash-and-centrifuge increases ROS formation without the selection benefits of gradient separation 3

Clinical Algorithm

1. For unexplained infertility: Use density gradient centrifugation (SpermGrad or similar silane-coated products) 1

2. For normozoospermia with normal parameters: Either density gradient centrifugation or swim-up is acceptable, though gradient may still be preferable 1

3. For oligozoospermia or asthenozoospermia: Use density gradient centrifugation exclusively 1

4. Centrifugation protocol: Use shorter duration (2 minutes preferred) at room temperature 1, 3