Letters to the editor |
Development of a novel home sperm test – What are the limitations?
1 Centro de Infertilidad Masculina Androgen, La Coruña, Spain 2 Harvard Medical School, Boston, MA and 3 Center for Advanced Research in Human Reproduction, Infertility and Sexual Function, Glickman Urological Institute, The Cleveland Clinic Foundation, Cleveland, OH, USA
4 To whom correspondence should be addressed at: E-mail: jalvarez{at}androgen.es
Sir,
I read with great interest the article by Bjorndahl et al. entitled ‘Development of a novel home sperm test’ published in the January 2006 issue of Human Reproduction.
The device is based on a lateral-flow immunoassay using an anti-CD59 antibody conjugated to colloidal gold to generate a visible red line when sperm are present. Progressively motile sperm from liquefied semen are separated by a direct swim-up through hyaluronic acid, and the sperm fraction from the swim-up reacts with the anti-CD59 antibody. The appearance of a clear red line, due to the colloidal gold label on the antibody-bound sperm, indicates a concentration of 10 x 106/ml or greater progressively motile sperm in semen.
CD59 is an 18–20 kDa GPI-linked glycoprotein thought to play a role in protecting cells from attack by complement (Rooney et al., 1993
). In addition to viable sperm, CD59 is also present in white blood cells, immature and dead sperm and in seminal plasma (Rooney et al., 1993). Separation of progressively motile sperm allows the detection of only progressively motile cells on the nitrocellulose strip, avoiding potentially erroneous results due to the presence of round spermatids, red blood cells or leukocytes in semen.
The study included 150 men selected from research donors (n = 132), subfertile males (n = 7) and post-vasectomy donors (n = 11). The subfertile males had an abnormal semen analysis, with a concentration of <10 x 106 progressively motile sperm per ml of semen. The concentration of progressively motile sperm, obtained by computer-assisted sperm analysis (CASA) (Hamilton Thorne, Beverley, MA, USA), and a modified Kremer test (hyaluronate migration test [HMT]) was performed on each semen sample. The results obtained from the device were compared with those for samples where the reference methods were concordant. Of the 150 subjects enrolled, five were excluded due to insufficient volume and a further two due to technical problems. For the comparison with the combined reference method (CASA and HMT), 14 subjects were excluded because the results of the two reference tests were not concordant.
The device gave a positive, red test line in 95 of the 129 valid experiments and no test line in the remaining 34. Of the 95 positive results, 91 (95.8%) also showed positive results with the reference tests, and of the 34 negative device results, 32 (94.1%) were negative in the reference tests. Thus, the device gave results with high sensitivity and specificity.
The authors concluded that the device provides an accurate, rapid and easily visualized estimate of the concentration of progressively motile sperm in a semen sample that can be used by a man in the comfort of his own home.
However, the authors should clarify the following points:
- The sample population used in this study is highly biased, since 88% of the semen samples were obtained from normal donors and only 5.3% from subfertile donors. In addition, the authors failed to mention what was the range of liquefaction times for the different semen samples tested. About 12% of semen samples produced by males undergoing infertility screening have high viscosity with liquefaction times above 60 min (Wilson and Bunge, 1975). Moreover, a significant proportion of these samples have liquefaction times ranging between 3 and 12 h post-ejaculation. Although semen viscosity could be reduced in the andrology laboratory by resorting to semen dilution or by inducing semen liquefaction with either enzymatic or non-enzymatic agents, this cannot be done at home by patients. As a result, should a representative subfertile and infertile male population be included in this study, a significant number of patients would not have been able to perform the test due to high semen viscosity. The assay time would have been 60 min or higher in 12% of the patients or more. A home sperm test with such a high rate of cancellations and high turnaround time would be obsolete.
- Semen viscosity will preclude users from accurately loading the semen sample into the sample port of the device. In addition, users will not know when the semen sample has liquefied and is ready to be loaded.
- A sine qua non condition for accuracy in semen analysis is sample homogeneity (de Ziegler et al., 1987). This is especially important when dealing with viscous samples from infertility patients. Therefore, in addition to exceedingly high turnaround analysis time, lack of sample homogeneity due to semen viscosity would produce inaccurate results.
- What is the cell-to-cell variability in the density of CD59 on the surface of spermatozoa recovered after the swim-up? This would be particularly important in teratozoospermic samples and in samples with a high proportion of sperm with residual cytoplasmic retention obtained from infertility patients. Cell-to-cell variability in CD59 density would result in inaccurate results.
The shortcomings related to semen viscosity could be circumvented by developing tests that accelerate semen liquefaction before sample loading like the case of FertilMARQ, the first FDA-approved home sperm test and the only test currently available in the market that incorporates this proprietary technology. However, since the signal produced by the authors’ device is based on the binding of an antibody to sperm, use of enzymatic or non-enzymatic agents that accelerate semen liquefaction would result in hydrolysis or denaturation of the antibody and CD59 epitopes on the surface of sperm, thus excluding this option.
In conclusion, although the device reported by Bjorndahl et al. (2006) could be used in a laboratory setting for the determination of motile sperm in washed semen samples, the application of this device to raw semen has severe limitations that make the device commercially nonviable as a home sperm test.
References
Rooney IA, Atkinson JP, Krul ES, Schonfeld G, Polakoski K, Saffitz JE, Morgan BP. (1993) Physiological relevance of the membrane attack complex inhibitory protein CD59 in human seminal plasma: CD59 is present on extracellular organelles (prostasomes), binds cell membranes and inhibits complement-mediated lysis. J Exp Med 177:1409–1420.
Wilson VB and Bunge RG. (1975) Infertility and semen non-liquefaction. J Urol 113:509–510.[Web of Science][Medline]
de Ziegler D, Cedars MI, Hamilton F, Moreno T, Meldrum DR. (1987) Factors influencing maintenance of sperm motility during in vitro processing. Fertil Steril 48:816–820.[Web of Science][Medline]
CiteULike 
Connotea 
Del.icio.us What's this?
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||