Are sperm counts declining? Or did we just change our spectacles?

Abstract

The popular and scientific debates about a possible decline in semen quality over the past decades are largely based on retrospective analyses of semen analysis data performed in the past. This article will argue that the conclusions from such analyses are significantly weakened because the methods of laboratory andrology have changed considerably since the 1950s. In the last 20–30 years, there have been significant developments in training and competence, increased emphasis on Quality Assurance (QA) and Quality Control (QC) as well as a major attempt at standardisation of technique through five successive editions of the World Health Organization (WHO) laboratory manuals. Interestingly, the only large prospective study carried out to date shows no change in sperm concentration over 15 years, being consistent with the idea that when laboratory methods are adequately controlled, no secular change in sperm counts are observed. In 1954, a High Court judge in the Court of Appeal of England and Wales made a landmark ruling that has become an important legal principle in English Tort law. It related to a case brought against the Minister of Health by two men who, 7 years earlier, had suffered paraplegia as a consequence of being given anaesthetic by lumbar puncture before a surgical procedure. While the precise details of the case are not really relevant to the topic of this paper, it is important to know that, unbeknown to the anaesthetists, the vials of anaesthetic had been contaminated in a manner that had not previously occurred, and could not be detected, before it was administered. Following the incident, clinical practice was immediately changed to prevent further occurrences. But, perhaps understandably, the two men sued for negligence and the matter was resolved in the courts. In his judgement, the Judge Lord Denning dismissed the men's claim saying, ‘We must not look at the 1947 incident with 1954 spectacles'.1 In effect, he was pointing out that we could not always view things that happened in the past with modern eyes. While this is now an important principle for lawyers, this paper will argue why it is also an important principle for interpreting whether or not we can establish if semen quality has been declining in recent years. When Elizabeth Carlsen and colleagues2 published their review of data from 61 papers published between 1938 and 1991, their regression analysis relied on the assumption that, during the 53 years in question, andrology laboratory methods had been wholly comparable and had remained unchanged. While they understandably excluded papers where sperm counting had been performed by computer-assisted methods or by flow cytometry (these methods were not widely used and were introduced only in later years), they recognized the apparent imprecision of counting sperm by other methods. However, they concluded that ‘there is no reason to believe that this test in itself has been subject to secular trend' and in support of this argument, they cited that ‘the same types of counting chambers have been used for the past 50 years by haematologists, who have not reported a similar secular trend in blood cell counts.' The issue of how accurate haematological methods may or may not have been in the past will be dealt with later in this paper. But it is fair to conclude that these arguments did not completely resonate with many at the andrology lab coalface. Their concern was highlighted only weeks later in the British Medical Journal,3 where Carlsen et al. were urged to ‘establish that their comparison of historical data is free of methodological bias'. To this day, this is a criticism that remains unresolved, both for the Carlsen et al.'s paper2 and those which have followed it (see Fisch4 for review). This opinion paper will argue that even with today's relatively well-standardized laboratory methods to assess semen quality, with well-established training programmes for laboratory staff, increased emphasis on laboratory accreditation and comprehensive internal and external quality assurance programmes in place, we are still far from generating consistent error-free data for semen analysis. As a consequence, it is very hard to look back into the archives with any sense of confidence about the precision and reliability of measurements made in the past. In effect, we are wearing the wrong spectacles. To set the scene, there are three areas of current and historical laboratory practice that need to be examined before the main arguments can be set out: (i) the development of semen analysis methodology; (ii) the selection and implementation of laboratory tests; and (iii) Quality Assurance (QA) and Quality Control (QC). Each will now be discussed in turn.