Introduction
A recent review proposed a guideline on the clinical utility of sperm DNA fragmentation
(SDF) testing presented by four clinical scenarios in an evidence-based approach (1).
This comprehensive review addressed commonly encountered clinical scenarios and provided
practice based recommendations. Furthermore, it tried to explain the current indications
of SDF testing as well as the management of increased SDF. Certainly, using clinical
scenarios will be a useful reference for assisting practicing physicians in identifying
the circumstances in which SDF testing is of greatest clinical value.
It is well accepted that the diagnostic potential of conventional semen analysis is
limited. However, semen analysis remains the first step and the cornerstone for evaluation
of male fertility. The American Urological Association (AUA) and the American Society
for Reproductive Medicine (ASRM) recommended a thorough primary assessment of the
infertile man that should contain a detailed medical and reproductive history, a physical
examination and no less than two semen analyses (2,3). A real concern is that around
15% of men with normal conventional semen analysis profiles still complain of infertility
which might be related to increased SDF (4,5). Many recent studies tried to address
this issue and investigated the possible correlation between SDF and conventional
sperm parameters (4,5).
Most of studies reported a reversed association between SDF rate and sperm quality
(6). On the contrary, several other studies were unable to demonstrate a significant
association between the conventional seminal variables, such as sperm concentration,
motility, vitality, morphology and SDF indices (7). The inconsistency among studies
regarding the correlations between conventional seminal variables and SDF indices
might be caused by several issues: (I) differences in the used procedures for DNA
integrity testing; (II) differences in the techniques and applied criteria for assessment
of the analysis of conventional semen parameters; (III) quality control in semen parameters
testing and (IV) the selection criteria of the studied populations are not usually
standardized (8,9).
Association between SDF and clinical parameters
Controversy exceeds the correlation between SDF and conventional sperm parameters
to surround other important clinical endpoints such as fertilization rates, embryonic
development, implantation, pregnancy and abortion rates and congenital anomalies of
the offspring (5,10). Although fertilization has been achieved even in the presence
of elevated SDF rates, it is generally believed that there is negative correlation
between fertilization and the presence of high levels of SDF (9).
Considerations regarding routine application of SDF assessment in clinical practice
Although the evaluation of the SDF indices are increasingly used in primary clinical
assessment as a unique indicator of male infertility. The sensitivity, specificity
and likelihood ratios of the available tests do not support its routine utilization
to estimate the probability of pregnancy in in-vitro fertilization (IVF) and intra-cytoplasmic
sperm injection (ICSI) cycles. On the other hand, the importance of SDF has been recognized
in the recent AUA and European Association of Urology guidelines on male infertility
(1,11,12). Hence, a more realistic approach should be adopted to identify the population
of infertile men who might benefit from this newly-emerged tool of fertility assessment
(13). Several studies have rationalized this diagnostic test in the following categories:
idiopathic infertile patients with significant morphologic abnormalities i.e., polymorphic
teratozoospermia, globozoospermia, large head syndrome, varicocele (9), lifestyle
factors, such as smoking (even passive smoking), obesity, diabetes mellitus (14),
testicular neoplasia specially that followed chemo- and/or radiotherapy, male carriers
of a structural chromosomal abnormality, infertile men who had low gestational rates
and low embryonic quality in ART, repeated ART failure, miscarriage and genital tract
infection (9).
In cases of unexplained male infertility, several conventional assessments of semen
revealed no abnormality in addition to the lack of female factor abnormality, SDF
may be of benefit. Sources of sperm with SDF include nuclear remodeling disorders
with spermatogenesis and other post-testicular factors. These disorders result in
increase of oxidative stress which ultimately lead to damage of the sperm DNA integrity.
A value above 25% of the SDF index signifies an acceptable threshold for higher chance
of miscarriage and pregnancy failure or longer duration till achieving pregnancy (15).
If the primary assessment indicates correctible etiology such as varicocele or leukocytospermia,
a prerequisite treatment for these etiologies should be offered, i.e., varicocelectomy
or antibiotic therapy. However, in the case of idiopathic infertility increased levels
of SDF may rationalize empirical treatment such as antioxidant therapy or lifestyle
modifications such as cessation of cigarette smoking, to possibly diminish the underlying
damage related to oxidative stress (9). Using testicular sperm rather than ejaculated
sperm in men with high SDF, oligozoospermia or recurrent IVF failure was reported
(16).
Debate: should SDF testing be offered to all infertile men with normal semen profiles?
On the one hand, most clinicians agree on the limitations of conventional semen analysis.
Since we have a more sensitive molecular test that looks at the paternal genome and
can detect molecular anomalies in sperm, why shouldn’t we use it as an adjunct to
the semen analysis? From the clinical stand point, several studies have shown that
about 25% of couples are diagnosed with idiopathic infertility as a result of the
limitations of current testing (17). Other studies had shown the benefits of SDF testing
and the solid effect of SDF testing on fertilization and early embryo quality (18).
If lifestyle modification and medical therapy do not result in achievement of natural
pregnancy, therefore, SDF testing may be the test we need to identify couples requiring
assisted reproductive technique (19). Certain categories of patient who may benefit
from SDF testing are patients who have been heavily exposed to toxicants or radiochemotherapies,
cancer patients even before they receive chemotherapy in whom the semen contain a
higher level SDF; diabetic patients; male partners of wives with repetitive, unexplained
pregnancy loss, or unexplained failure of fertilization (20).
On the other hand, although SDF testing is a promising tool in the evaluation of male
infertility, from a consensus point of view, there is still lack of strong evidence
for its predictive value thus hindering its recommendation for universal adoption.
The problem seems to be mainly related to the characteristics of available studies,
which included small and heterogeneous populations and used different methods for
SDF testing (21). Furthermore, the American Society for reproductive Medicine Practice
Committee guidelines endorsed that more research is needed to reach a final conclusion.
In addition, this testing is expensive and, in most of the world, the cost is carried
out by the patient (22). Thus, it is hard to confidently reach to a consensus agreement
that routine SDF testing is mandatory in evaluation of every infertile male (20).
Conclusions and perspective
The authors had summarized information from numerous previous studies and organized
clear and practical guidelines in the format of clinical case scenarios. The suggestions
and recommendations are truly valid and provide insight into the clinical circumstances
in which the assessment of SDF testing may be crucial. In light of the scientific
accumulated data, the coming years may witness additional large scale clinical trials
before the available standardized detailed tools of SDF assessment can be fully incorporated
in routine clinical practice. Certainly, various important issues such as optimal
assay, protocols applied and thresholds of the clinical relevance and prognostic value
of SDF assessment are in need for a global consensus.
A conventional semen analysis is still considered the gold standard of male fertility
evaluation especially with the availability of universally accepted rigorous methodology
to perform the analysis. The current tools for investigating male factor infertility
is still far from ideal however, there is promising novel technology and innovative
modalities to improve the well-established diagnostic tools for male infertility.
A holistic approach for diagnosis of male factor infertility should be adopted. Physicians
may need to review all data in patient’s chart during the routine diagnostic workup
and the data gained form routine seminal assessment in addition to the SDF testing
if available. We expect to witness new methods and technologies that may revolutionize
and optimize diagnosis and management of certain etiologies of male factor infertility.
The vision of diagnosing spermatozoal genomic integrity in a routine diagnostic male
infertility workup may become true in the near future.