世界卫生组织的男性生育力判断标准受到质疑

研究显示精子形态学是最佳的决定因数

  2001年11月7日-根据11月8日《新英格兰医学杂志》的最新研究报导:根据精液分析,世界卫生组织对男性不孕的判断标准提出疑问。以前许多被认为生育能力正常的男性,其实可能生育会有困难,而有些根据目前诊断标准被确定生育力异常的人,实际上却可能有生育能力。

  国家儿童保健和人类发展研究所所长,Duane Alexander医师在一次记者会上说到:这些新的研究为男性生殖能力的评估提供了更多可靠的方法。

  Alexander说道:对于原因不明不孕夫妇的特殊治疗是一有价值的研究,它使医师调整其治疗方案,以决定治疗重点应集中在妇女还是在男性上。

  该研究的受试者包括:不孕夫妇中的765名男性和生育正常夫妇中的696名男性,他们来自9个不同的美国医学中心,每位受试者均采集精液样本2份。其年龄为20-55岁。如果其配偶在最近两年内怀孕则诊断?生育力正常。

  虽然世界卫生组织标准阐明正常男性精液中精子数每毫升须大于二亿个精子,活动能力须超过50%,该研究显示,如果男性的精液中精子数每毫升有四亿八千万个精子,精子活动能力超过63%,且超过12%的精子形态正常,则一般多将其诊断为生育力。

  男性生育力的“临界区”,即男性仍然可能生育,其精液中所含精子数为每毫升一亿三千五百万至四亿八千万,精子活动能力大于63%,其中12%以上的精子形态学正常。如果其精液所含精子数每毫升小于一亿三千五百万,活动能力小于32%,形态学正常的精子数小于9%,则该男性很有可能被诊断为不育。

  正如该研究报导中所述,其它两项研究对世界卫生组织参考值的精确性提出了质疑。在该项研究中,虽然每份精液的各种评估指标对于区别不育和生育力正常有帮助,但是没有一个是一项很好的指证,或者具有极强的诊断价值。形态学正常的精子百分数的诊断价值最强。

  在一次记者会上,该研究的作者,纽约Rochester大学医学中心的妇产科学主任,David Guzick医师说到:对于不育的治疗,都建立在最初所确立的何谓正常及何谓异常的观点上,到目前为止,我们刚开始意识到不能用固定僵化的标准来对患者进行测试。在诊断不育夫妇和采取相对应治疗措施时,我们希望专家们能够应用其修订版内所提到的概念。

  Guzick还提到:精液的分析往往是使用计算机进行的,但是不孕患者却不能只这样做,很有必要再做一些补充的分析检查。研究结果显示形态学评估结果是区分不育和生育力正常的最佳手段。

  附Salynn Boyles报告

WHO Standards for Male Fertility Questioned

Study Shows Sperm Morphology Is Best Determinant

By Laurie Barclay, MD
WebMD Medical News

Reviewed by Michael W. Smith, MD

Nov. 7, 2001 -- New recommendations published in the Nov. 8 issue of The New England Journal of Medicine question current WHO standards of male fertility based on semen analysis. While many men formerly considered fertile may have difficulty fathering a child, others considered abnormal by current standards may actually be fertile.

"These recommendations provide a more reliable means for estimating the likelihood of a man's fertility," Duane Alexander, MD, says in a news release. He is director of the National Institute of Child Health and Human Development.

"This will prove a valuable tool for specialists treating couples with unexplained infertility, allowing them to make their best judgment on whether it would be more helpful to focus on treatment for the man or the woman," Alexander says.

The research team analyzed two semen samples from each of 765 men in infertile couples and 696 men in fertile couples from nine different U.S. centers. The men ranged in age from 20 to 55, and were considered fertile if their partner had conceived within the last two years.

Although WHO criteria state that normal semen contains >20 million sperm/mL, with >50% motility, this study showed that men were most likely to be fertile if their semen had >48 million sperm/mL, >63% motility, and >12% of sperm having normal morphology.

The "gray zone" of borderline fertility in which men could still father a child had sperm counts between 13.5 and 48 million sperm/mL, >63% motility, and >12% percent of sperm with normal morphology. Men were most likely to be infertile if their semen contained <13.5 million sperm/mL, <32% motility, and <9% of sperm with normal morphology.

As the article points out, two other studies have questioned the accuracy of the WHO reference values. Although each of the sperm measurements helped to distinguish between fertile and infertile men in this study, none was a powerful discriminator or diagnostic in and of itself. The percentage of sperm with normal morphologic features had the greatest discriminatory power.

"Every treatment for infertility depends upon first establishing what's normal and abnormal," says lead author David Guzick, MD, chairman of obstetrics and gynecology at the University of Rochester Medical Center in New York, in a news release. "Up until now, we've just been using guidelines without rigorously testing them. We hope specialists will use these revisions in their counseling of infertile couples and in tailoring treatments to individual patient circumstances."

"Semen analysis is routinely done using a computer, but you couldn't do that in this case," he says. "So It would probably be very costly to implement. But our findings suggest that assessing morphology is the best discriminator of fertility and infertility," Guzick tells WebMD.

With reporting by Salynn Boyles

© 2001 WebMD Corporation. All rights reserved.

    
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