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Making sense of PSA and ejaculation


What is the prostate gland for? Its principal physiological function is to manufacture the fluid that nurtures spermatozoa. What happens to one of its principle prostate-specific proteins in serum upon ejaculation might seem a sensible first step in sorting out the use of a serum test. Given that PSA is often measured, that thousands of papers are published on PSA each year, and millions of tests done, one might think that the effects of basic physiological changes would be well sorted out. Not so.

When an assay is just a guess

To answer the question about the effect on PSA of ejaculation, it is necessary to enter the arcane world of immunoassays and their properties.

Any assay is designed to measure something within certain concentration limits. For most common PSA assays, this means values between about 1 to 100 µg/L. Samples with higher concentrations can be diluted to be within this range. But concentrations of less than 1 µg/L are in a part of the assay where significant inaccuracies can be expected, and below about 0.5 µg/L any value obtained is little better than a guess (though there are some `super-sensitive' assays which can measure very low values). Many of the articles examine populations with very low PSA levels.

What is the question?

PSA will be measured in many clinical situations (like after operation for prostate cancer) where ejaculation is unlikely to be an issue. But where prostate cancer is just a suspicion a serum PSA might well be part of the diagnostic regimen in a man who is sexually active. Knowing whether and how ejaculation affects serum PSA will be important. We are most concerned with effects in older men (over 50) who have, and who do not have, prostate cancer or benign hyperplasia, because these are the people most likely to be tested. How long after ejaculation do any effects last? That will affect the interpretation and usefulness of the test.

Many articles look only at young men, and at times early after ejaculation. Those that look at older men generally exclude those with prostatic disease.

Where's the evidence?

Bandolier performed a MEDLINE search for papers which examined ejaculation and serum PSA. We found nine. The details are shown in the Table. None of the articles commented on the ability of the assays used to measure low values of PSA.

Effects of ejaculation on serum PSA
Reference Population Abstinence period Mean baseline PSA (µg/L) PSA Method Assay sensitivity Post-ejaculation assay times Results Bandolier 's judgement
Younger men
Glenski et al, 1992 30 men 22-30 years not stated 0.55 Tandem-R not stated 1 day no change invalid
Simak et al, 1993 18 men 20-39 years 4 days 1.4 Tandem-E not stated 1 day, 7 days 85% fall at 1 day, and about 70% at 7 days valid
Kirkalt et al, 1995 19 men 21-25 years none stated 0.75 Tandem-E not stated 1-5 days 1 µg/L all showed falls of ≥ 50% at some time over 5 days invalid
Heidenreich et al,1997 100 men 25-35 years 4 days 0.85 Tandem not stated 1 hour, 1 day no change valid
Zisman et al, 1997 25 men 20-45 years 3 days 0.9 Roche not stated 1 hour increase invalid
Older men  
McAleer et al,1993 35 men 40-86 years none stated 1.74 Tandem -R not stated 1 day no change invalid
Tchetgen et al,1996 64 men 49-79 years 7 days range <1 to 13 probably IMx not stated 1, 6 and 24 hours increase in PSA, with larger increases for higher baseline PSA valid
Rodrigues et al,1996 40 men 50-60 years 3 days 1.7 Tandem-R not stated 1 day, 7 days no change valid
Herschman et al,1997 22 men 51-67 years 1 day 1.3 Tandem-E not stated 1, 6 and 24 hours increase at 1 hour, but not 1 day valid
No report made any statement about analytical accuracy at low levels of PSA
In order to help sort wheat from chaff, we made a decision as to whether the studies were valid or not. Invalid articles were defined as those which had only men with very low serum PSA concentrations (less than 0.6 µg/L), those which made no statement about abstinence from intercourse before the study, or those which had measurements only at very short times after ejaculation. Four studies were invalidated by these criteria. For the remaining five, the results can be looked at by age (we chose an arbitrary cut off of about 40 years) and by PSA concentration.

Younger men

All the studies had men with very low PSA concentrations. Of the two valid studies, one showed a large decrease at one day, and one showed no change. One study invalidated because of no stated abstinence period before the study started also showed large decreases in all men with PSA values above 1 µg/L over five days.

Older men

None of the studies included men with prostate cancer known or suspected and only one included men with higher concentrations of PSA. Three valid studies showed increases or no change in serum PSA after ejaculation. Increases, when seen, tended to be at earlier times (hours rather than days). The study which examined how changes in PSA were related to baseline concentrations demonstrated greater increases with higher baseline values.

Comment

A complicated story which perhaps serves to demonstrate how difficult it is to get a simple answer to a simple question. The variabilities of assay performance, age and baseline PSA concentration have largely been ignored. What seems to be the answer is that there may ( and this is a big may ) be falls in PSA after ejaculation in men below about 45 years over one to five days, but rises in older men. What evidence there is suggests that rises are greater with higher baseline PSA and that they last for perhaps one or two days. We still have no idea of the effect of ejaculation in men with prostate pathology.

Men having blood taken for PSA should be advised to abstain from intercourse for several days before, or at least be questioned about the time since their last ejaculation.

References:

  1. WJ Glenski, GG Klee, EJ Bergstralh, JE Oesterling. Prostate-specific antigen: establishment of the reference range for the clinically normal prostate gland and the effect of digital rectal examination, ejaculation, and time on serum concentrations. The Prostate 1992 21: 99-110.
  2. R Simak, S Maderbascher, Z Zhang, U Maier. The impact of ejaculation on serum prostate specific antigen. Journal of Urology 1993 150: 895-7.
  3. Z Kirkalt, G Kirkalt, A Esen. Effect of ejaculation on prostate specific antigen levels in normal men. European Urology 1995 27: 292-4.
  4. A Heidenreich, R Vorreuther, S Neubauer et al. The influence of ejaculation on serum levels of prostate specific antigen. Journal of Urology 1997 157: 209-11.
  5. A Zisman, Y Soffer, Y Seigel et al. Postejeculation prostate specific antigen level. European Urology 1997 32: 54-7.
  6. JK McAleer, LW Gerson, D McMahon, L Geller. Effect of digital rectal examination and ejaculation on serum prostate specific antigen after twenty-four hours. Urology 1993 41: 111-2.
  7. M Tchetgen, J Song, M Strawderman et al. Ejaculation increases the serum prostate specific antigen concentration. Urology 1996 47: 511-6.
  8. N Netto, F Apuzzo, E de Andrade et al. The effects of ejaculation on serum prostate specific antigen. Journal of Urology 1996 155: 1329-31.
  9. J Herschman, D Smith, W Catalona. Effect of ejaculation on serum total and free prostate specific antigen concentrations. Urology 1997 50: 239-43.



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