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R B Donker, V Vloeberghs, H Groen, H Tournaye, C M A van Ravenswaaij-Arts, J A Land, Chromosomal abnormalities in 1663 infertile men with azoospermia: the clinical consequences, Human Reproduction, Volume 32, Issue 12, December 2017, Pages 2574–2580, https://doi.org/10.1093/humrep/dex307
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Abstract
What is the prevalence of chromosomal abnormalities in azoospermic men and what are the clinical consequences in terms of increased risk for absent spermatogenesis, miscarriages and offspring with congenital malformations?
The prevalence of chromosomal abnormalities in azoospermia was 14.4%, and the number of azoospermic men needed to be screened (NNS) to identify one man with a chromosomal abnormality with increased risk for absence of spermatogenesis was 72, to prevent one miscarriage 370–739 and to prevent one child with congenital malformations 4751–23 757.
Infertility guidelines worldwide advise screening of non-iatrogenic azoospermic men for chromosomal abnormalities, but only few data are available on the clinical consequences of this screening strategy.
This retrospective multicentre cross-sectional study of non-iatrogenic azoospermic men was performed at the University Hospital Brussels, Belgium, and the University Medical Centre Groningen, The Netherlands, between January 2000 and July 2016.
Analysis of clinical registries retrospectively identified 1663 non-iatrogenic azoospermic men with available results of karyotyping and FSH serum levels. Iatrogenic azoospermia was an exclusion criterion, defined as azoospermia after spermatotoxic medical treatment, exogenous androgen suppletion or vasectomy and/or vasovasostomy. Also, men with a clinical diagnosis of anejaculation or hypogonadotropic hypo-androgenism and/or FSH values <1.0 U/l were excluded. Chromosomal abnormalities were categorized according to their (theoretical) impact on clinical consequences for the patient (i.e. an increased risk for absence of spermatogenesis) and adverse pregnancy outcomes (i.e. miscarriage or offspring with congenital malformations), in both normogonadotropic (FSH < 10 U/l) and hypergonadotropic (FSH ≥ 10 U/l) azoospermia. We estimated the NNS for chromosomal abnormalities to identify one man with absence of spermatogenesis and to prevent one miscarriage or one child with congenital malformations, and calculated the surgical sperm retrieval rates per chromosomal abnormality.
The overall prevalence of chromosomal abnormalities in azoospermia was 14.4% (95% CI 12.7–16.1%), its prevalence being higher in hypergonadotropic azoospermia (20.2%, 95% CI 17.8–22.7%) compared to normogonadotropic azoospermia (4.9%, 95% CI 3.2–6.6%, P < 0.001). Klinefelter syndrome accounted for 83% (95% CI 77–87%) of abnormalities in hypergonadotropic azoospermia. The NNS to identify one man with increased risk for absence of spermatogenesis was 72, to prevent one miscarriage 370–739, and to prevent one child with congenital malformations 4751–23 757. There was no clinically significant difference in NNS between men with normogonadotropic and hypergonadotropic azoospermia. The surgical sperm retrieval rate was significantly higher in azoospermic men with a normal karyotype (60%, 95% CI 57.7–63.1%) compared to men with a chromosomal abnormality (32%, 95% CI 25.9–39.0%, P < 0.001). The sperm retrieval rate in Klinefelter syndrome was 28% (95% CI 20.7–35.0%).
The absolute number of chromosomal abnormalities associated with clinical consequences and adverse pregnancy outcomes in our study was limited, thereby increasing the role of chance. Further, as there are currently no large series on outcomes of pregnancies in men with chromosomal abnormalities, our conclusions are partly based on assumptions derived from the literature.
The NNS found can be used in future cost-effectiveness studies and the evaluation of current guidelines on karyotyping in non-iatrogenic azoospermia.
None to declare.
Introduction
Male factor infertility is a frequent cause of infertility, with azoospermia found in 10–16% of infertile couples (Tournaye et al., 2017a). While the cause of azoospermia often remains unknown, both genetic and environmental factors can result in spermatogenic impairment and obstructive azoospermia. With regard to genetic causes, both chromosomal abnormalities identifiable by karyotype analysis and gene mutations or submicroscopic deletions of the Y chromosomal azoospermia factor (AZF) region can disrupt spermatogenesis (Martin, 2008; Morin et al., 2017; Tournaye et al., 2017a), while CFTR mutations are associated with obstructive azoospermia (Jiang et al., 2017).
In azoospermic patients a prevalence of chromosomal aberrations between 15% and 25% has been reported, depending on the subgroup of azoospermic men studied (Vincent et al., 2002; Dul et al., 2012a; Shin et al., 2016; Takeda et al., 2017; Tournaye et al., 2017a). Abnormal karyotypes may have clinical consequences for the patients themselves as well as for their potential offspring. Firstly, specific gonosomal chromosomal abnormalities comprise AZF deletions that are associated with absence of spermatogenesis (Martin, 2008; Tournaye et al., 2017a), and surgical sperm retrieval should not be performed in these patients. Moreover, only few studies to date have investigated the outcome of sperm retrieval in men with other chromosomal abnormalities (Cissen et al., 2016; Corona et al., 2017; Takeda et al., 2017). Secondly, specific chromosomal abnormalities, in particular balanced chromosomal rearrangements, are associated with increased risk of miscarriage or offspring with congenital malformations. The risk of an unbalanced karyotype depends on the segregation behaviour of the derivative chromosomes during meiosis and the size and nature of the translocated or inverted chromosomal segments (Midro et al., 1992; Morin et al., 2017).
Current guidelines unanimously advise screening of (non-iatrogenic) azoospermic men for chromosomal abnormalities (AUA and ASRM, 2006; EAU, 2012; NVOG, 2015; NICE, 2016; Ventimiglia et al., 2016). However, these recommendations are based upon reported estimates of identifying a karyotype abnormality in azoospermic men, while no effectiveness studies are available on this screening strategy with regard to clinical consequences or adverse pregnancy outcomes. However, these recommendations are not based on clinical data, because there are no available effectiveness studies of this screening strategy in (subgroups of) azoospermic men with regard to clinical consequences or adverse pregnancy outcomes. We previously showed for non-azoospermic infertile men that the number needed to be screened (NNS) by chromosomal testing to prevent one miscarriage was 315–347 and the NNS to prevent one child with congenital malformations was 2543–12 723 (Dul et al., 2012b). However, based on a small number of azoospermic men in this previous study (79 men, of whom 12 had an abnormal karyotype), our data suggested that the NNS to prevent these adverse pregnancy outcomes might be more favourable in azoospermia compared to oligospermia (Dul et al., 2012b).
Therefore, the aim of this study was to evaluate screening for chromosomal abnormalities in non-iatrogenic azoospermia with regard to clinical consequences (i.e. an increased risk for absence of spermatogenesis) and the prevention of miscarriage or offspring with congenital malformations.
Materials and Methods
Patients
We performed a retrospective multicentre cross-sectional study in unselected azoospermic men of consecutive infertile couples attending the two participating fertility clinics. The study includes all patients presenting with non-iatrogenic azoospermia and/or undergoing surgical sperm extraction because of non-iatrogenic azoospermia at the University Hospital of Brussels, Belgium, from January 2000 until July 2016, and at University Medical Centre Groningen (UMCG), The Netherlands, from January 2008 until July 2016. The shorter UMCG inclusion period was selected to exclude the cohort of azoospermic men described earlier by Dul et al. (2012a, 2012b). Data were collected by chart review and were analysed anonymously.
All men included in the study presented in the participating fertility clinics, were at least 18 years of age at presentation, were diagnosed with non-iatrogenic azoospermia in at least two semen analyses (with at least one of these semen analyses performed in one of the participating fertility clinics), and had karyotyping and FSH serum level results available. Men with clinical diagnosis of anejaculation or hypogonadotropic hypoandrogenic status and/or FSH values <1.0 U/l were excluded. Iatrogenic azoospermia was excluded and defined as azoospermia after spermatotoxic medical treatment (e.g. chemotherapy, radiotherapy), exogenous androgen suppletion (e.g. testosterone, anabolic steroids), or status after vasectomy and/or vasovasostomy. Normogonadotropic azoospermia was defined as FSH <10 U/l and hypergonadotropic azoospermia as FSH ≥10 U/l (AUA and ASRM, 2006; NVOG, 2015). Moreover, patients with rare syndromes known to be associated with male infertility were excluded (Beckwith–Wiedemann syndrome, Marfan syndrome, ADPKD, M. Steinert, VATER association, Townes–Brocks syndrome). All available data were collected on concomitant AZF deletions (n = 1144/1663, i.e. 69%), clinically estimated testis volume (n = 1441/1663, i.e. 87%), and surgical sperm retrieval attempts and outcomes (n = 1450/1663, i.e. 87%).
Surgical sperm retrieval was performed by fine needle aspiration, percutaneous epididymal sperm aspiration, microsurgical epididymal sperm aspiration and/or conventional or micro-testicular sperm extraction, according to previously described protocols in the two participating fertility clinics (Vloeberghs et al., 2015; Tournaye et al., 2017b).
Chromosomal, sperm and hormone analyses
For this study, chromosomal abnormalities were defined as aberrations detected by conventional (microscopic) karyotyping with a minimal resolution of 550 bands. The karyotyping procedure, sperm analysis, and measurement of serum FSH levels were performed as described previously (Dul et al., 2012a). Analysis of AZF deletions was performed by PCR in parallel with karyotyping. For karyotypes with an increased risk for an AZF deletion, the AZF region was studied by either PCR or FISH.
Genetic risk analysis
For each abnormality found, we performed a literature search for clinical consequences, specifically the likelihood of absolute absence of spermatogenesis or the chance of transmitting a chromosomal imbalance to the progeny that may lead to miscarriage and/or offspring with congenital anomalies. The estimation of the risk of unbalanced offspring was based on published data on the expected segregation pattern of the translocation chromosomes and viability of the respective deletions and duplications (Midro et al., 1992; Schinzel, 2001; Feenstra et al., 2006). Based on these publications, we categorized the detected chromosomal abnormalities into the following clinical reference groups, according to theoretical risk of adverse outcome: no clinical relevance, absolute absence of spermatogenesis, increased risk for miscarriage, and/or increased risk for congenital abnormality.
Statistical analysis
Statistical analysis was carried out using the Statistical Package for the Social Sciences version 23 for Windows (SPSS Inc., Chicago, IL, USA). Data were described in absolute counts and proportions. NNS were calculated by dividing the number of subjects in the reference group by the number of patients at risk. Associations were assessed by Chi-squared tests and univariate binary logistic regression. Results were considered statistically significant when P < 0.05.
Institutional review board approval
The study was approved by the local Ethics Committees of the Free University of Brussels and the UMCG.
Results
Prevalence of chromosomal abnormalities in azoospermia
The prevalence of chromosomal abnormalities in non-iatrogenic azoospermic men was 14.4% (240/1663, 95% CI 12.7–16.1%), with Klinefelter syndrome accounting for 73% (176/240, 95% CI 68–79%) of all chromosomal abnormalities (Table I). The prevalence of chromosomal abnormalities was higher in hypergonadotropic azoospermia, 20.2% (209/1033, 95% CI 17.8–22.7%), compared to 4.9% in normogonadotropic azoospermia (31/630, 95% CI 3.2–6.6%, P < 0.001). Klinefelter syndrome accounted for 83% (172/209, 95% CI 77–87%) of abnormalities in hypergonadotropic azoospermia. Of Klinefelter men, 98% (172/176, 95% CI 96–100%) were hypergonadotropic, and they explain most of the difference in chromosomal abnormality prevalence between normogonadotropic and hypergonadotropic men. For all azoospermic men the NNS to identify one chromosomal abnormality was 7. For normogonadotropic azoospermic men it was 20 and for hypergonadotropic azoospermic men it was 5. All individual chromosomal abnormalities found are presented in Supplementary Table I.
. | Normal karyotype . | Abnormal karyotype . | Abnormal karyotype category . | |||||
---|---|---|---|---|---|---|---|---|
Klinefelter* . | Gonosomal (non-Klinefelter) . | Autosomal reciprocal translocation . | Autosomal Robertsonian translocation . | Translocation involving gonosomes . | Remaining category** . | |||
Chromosomal abnormalities | ||||||||
Azoospermia (n = 1663) | 85.6 (1423) | 14.4 (240) | 10.5 (176) | 1.7 (28) | 0.7 (12) | 0.7 (11) | 0.5 (9) | 0.2 (4) |
Normogonadotropic azoospermia (n = 630) | 95.1 (599) | 4.9 (31) | 0.6 (4) | 1.4 (9) | 1.0 (6) | 0.3 (2) | 1.1 (7) | 0.5 (3) |
Hypergonadotropic azoospermia (n = 1033) | 79.8 (824) | 20.2 (209) | 16.7 (172) | 1.8 (19) | 0.6 (6) | 0.9 (9) | 0.2 (2) | 0.1 (1) |
Surgical sperm retrieval rate | ||||||||
Azoospermia (n = 1450) | 60 (757/1253) | 32 (64/197) | 28 (42/151) | 27 (4/15) | 45 (5/11) | 70 (7/10) | 43 (3/7) | 100 (3/3) |
Normogonadotropic azoospermia (n = 567) | 78 (425/542) | 56 (14/25) | 25 (1/4) | 50 (3/6) | 50 (3/6) | 100 (2/2) | 60 (3/5) | 100 (2/2) |
Hypergonadotropic azoospermia (n = 883) | 47 (332/711) | 29 (50/172) | 28 (41/147) | 11 (1/9) | 40 (2/5) | 63 (5/8) | 0 (0/2) | 100 (1/1) |
. | Normal karyotype . | Abnormal karyotype . | Abnormal karyotype category . | |||||
---|---|---|---|---|---|---|---|---|
Klinefelter* . | Gonosomal (non-Klinefelter) . | Autosomal reciprocal translocation . | Autosomal Robertsonian translocation . | Translocation involving gonosomes . | Remaining category** . | |||
Chromosomal abnormalities | ||||||||
Azoospermia (n = 1663) | 85.6 (1423) | 14.4 (240) | 10.5 (176) | 1.7 (28) | 0.7 (12) | 0.7 (11) | 0.5 (9) | 0.2 (4) |
Normogonadotropic azoospermia (n = 630) | 95.1 (599) | 4.9 (31) | 0.6 (4) | 1.4 (9) | 1.0 (6) | 0.3 (2) | 1.1 (7) | 0.5 (3) |
Hypergonadotropic azoospermia (n = 1033) | 79.8 (824) | 20.2 (209) | 16.7 (172) | 1.8 (19) | 0.6 (6) | 0.9 (9) | 0.2 (2) | 0.1 (1) |
Surgical sperm retrieval rate | ||||||||
Azoospermia (n = 1450) | 60 (757/1253) | 32 (64/197) | 28 (42/151) | 27 (4/15) | 45 (5/11) | 70 (7/10) | 43 (3/7) | 100 (3/3) |
Normogonadotropic azoospermia (n = 567) | 78 (425/542) | 56 (14/25) | 25 (1/4) | 50 (3/6) | 50 (3/6) | 100 (2/2) | 60 (3/5) | 100 (2/2) |
Hypergonadotropic azoospermia (n = 883) | 47 (332/711) | 29 (50/172) | 28 (41/147) | 11 (1/9) | 40 (2/5) | 63 (5/8) | 0 (0/2) | 100 (1/1) |
*Mosaic and non-mosaic Klinefelter syndrome.
**Inversions, autosomal ring chromosome, autosomal marker chromosome.
Data are % (n) (white rows) or % (n with sperm recovered/n operated) (grey rows).
. | Normal karyotype . | Abnormal karyotype . | Abnormal karyotype category . | |||||
---|---|---|---|---|---|---|---|---|
Klinefelter* . | Gonosomal (non-Klinefelter) . | Autosomal reciprocal translocation . | Autosomal Robertsonian translocation . | Translocation involving gonosomes . | Remaining category** . | |||
Chromosomal abnormalities | ||||||||
Azoospermia (n = 1663) | 85.6 (1423) | 14.4 (240) | 10.5 (176) | 1.7 (28) | 0.7 (12) | 0.7 (11) | 0.5 (9) | 0.2 (4) |
Normogonadotropic azoospermia (n = 630) | 95.1 (599) | 4.9 (31) | 0.6 (4) | 1.4 (9) | 1.0 (6) | 0.3 (2) | 1.1 (7) | 0.5 (3) |
Hypergonadotropic azoospermia (n = 1033) | 79.8 (824) | 20.2 (209) | 16.7 (172) | 1.8 (19) | 0.6 (6) | 0.9 (9) | 0.2 (2) | 0.1 (1) |
Surgical sperm retrieval rate | ||||||||
Azoospermia (n = 1450) | 60 (757/1253) | 32 (64/197) | 28 (42/151) | 27 (4/15) | 45 (5/11) | 70 (7/10) | 43 (3/7) | 100 (3/3) |
Normogonadotropic azoospermia (n = 567) | 78 (425/542) | 56 (14/25) | 25 (1/4) | 50 (3/6) | 50 (3/6) | 100 (2/2) | 60 (3/5) | 100 (2/2) |
Hypergonadotropic azoospermia (n = 883) | 47 (332/711) | 29 (50/172) | 28 (41/147) | 11 (1/9) | 40 (2/5) | 63 (5/8) | 0 (0/2) | 100 (1/1) |
. | Normal karyotype . | Abnormal karyotype . | Abnormal karyotype category . | |||||
---|---|---|---|---|---|---|---|---|
Klinefelter* . | Gonosomal (non-Klinefelter) . | Autosomal reciprocal translocation . | Autosomal Robertsonian translocation . | Translocation involving gonosomes . | Remaining category** . | |||
Chromosomal abnormalities | ||||||||
Azoospermia (n = 1663) | 85.6 (1423) | 14.4 (240) | 10.5 (176) | 1.7 (28) | 0.7 (12) | 0.7 (11) | 0.5 (9) | 0.2 (4) |
Normogonadotropic azoospermia (n = 630) | 95.1 (599) | 4.9 (31) | 0.6 (4) | 1.4 (9) | 1.0 (6) | 0.3 (2) | 1.1 (7) | 0.5 (3) |
Hypergonadotropic azoospermia (n = 1033) | 79.8 (824) | 20.2 (209) | 16.7 (172) | 1.8 (19) | 0.6 (6) | 0.9 (9) | 0.2 (2) | 0.1 (1) |
Surgical sperm retrieval rate | ||||||||
Azoospermia (n = 1450) | 60 (757/1253) | 32 (64/197) | 28 (42/151) | 27 (4/15) | 45 (5/11) | 70 (7/10) | 43 (3/7) | 100 (3/3) |
Normogonadotropic azoospermia (n = 567) | 78 (425/542) | 56 (14/25) | 25 (1/4) | 50 (3/6) | 50 (3/6) | 100 (2/2) | 60 (3/5) | 100 (2/2) |
Hypergonadotropic azoospermia (n = 883) | 47 (332/711) | 29 (50/172) | 28 (41/147) | 11 (1/9) | 40 (2/5) | 63 (5/8) | 0 (0/2) | 100 (1/1) |
*Mosaic and non-mosaic Klinefelter syndrome.
**Inversions, autosomal ring chromosome, autosomal marker chromosome.
Data are % (n) (white rows) or % (n with sperm recovered/n operated) (grey rows).
Chromosomal abnormalities with an increased risk for absence of spermatogenesis
As listed in Supplementary Table I, 16 (non-Klinefelter) gonosomal chromosomal abnormalities included an AZF deletion with known absence of spermatogenesis. Thus, in our azoospermic cohort the prevalence of an abnormal karyotype that included AZF deletions associated with absence of spermatogenesis was 1.0% (16/1663, 95% CI 0.5–1.4%). When only considering results of karyotype testing, without further information on concomitant AZF deletions, 23 of the 240 (9.6%, 95% CI 5.9–13.3%) abnormal karyotypes were associated with an increased risk for an AZF deletion. Therefore, in azoospermia, the NNS to identify one man with a karyotype abnormality associated with increased risk for absence of spermatogenesis was 72 (prevalence 23/1663, 1.4%, 95% CI 0.8–1.9%). For normogonadotropic azoospermia it was 90 (prevalence 7/630, 1.1%, 95% CI 0.3–1.9%) and for hypergonadotropic azoospermia it was 65 (prevalence 16/1033, 1.6%, 95% CI 0.8–2.3%).
Chromosomal abnormalities in relation to adverse pregnancy outcomes
In azoospermia the prevalence of chromosomal abnormalities that result in an increased risk for miscarriage was 2.2% (36/1663, 95% CI 1.5–2.9%) and the prevalence of abnormalities that increased risk for offspring with congenital malformations was 1.7% (28/1663, 95% CI 1.1–2.3). Translocations (reciprocal, Robertsonian and gonosomal) accounted for 86% of chromosomal abnormalities with an increased risk for miscarriage and 89% of abnormalities with an increased risk for offspring with congenital anomalies (Supplementary Table I). Clinical characteristics of azoospermic men with and without a chromosomal abnormality associated with increased risk for miscarriage or offspring with congenital anomalies are shown in Supplementary Table II. In normogonadotropic azoospermia the prevalence of chromosomal abnormalities resulting in an increased risk for miscarriage was 2.9% (18/630, 95% CI 1.6–4.2%), and for offspring with congenital malformations it was 2.4% (15/630, 95% CI 1.2–3.6). In hypergonadotropic azoospermia the prevalence was 1.7% (18/1033, 95% CI 0.9–2.5%) for increased risk for miscarriage and 1.3% (13/1033, 95% CI 0.6–1.9%) for offspring with congenital malformations.
To calculate the NNS to prevent one miscarriage or one child with congenital anomalies (above the background risk for these adverse pregnancy outcomes), we conservatively estimated the sperm retrieval rate at 50% and subsequent live birth rate after ICSI with surgically retrieved sperm at 50%, based on our study data (Table I) and previous reports (Cissen et al., 2016; Vloeberghs et al., 2015; Meijerink et al., 2016; Corona et al., 2017; Takeda et al., 2017; Tournaye et al., 2017b). Moreover, for the chromosomal abnormalities found in our study, the mean risk for miscarriage and offspring with congenital abnormalities was estimated at 25–50% and 1–5%, respectively, based on our study data (Supplementary Table I) and on previous reports (Midro et al., 1992; Schinzel, 2001; Feenstra et al., 2006; Morin et al., 2017). Applying these assumptions, the NNS to prevent one miscarriage or one child with congenital abnormalities was calculated at 370–739 and 4751–23 757, respectively from least to most favourable estimate (Fig. 1). In normogonadotropic azoospermia the NNS to prevent one miscarriage or one child with congenital abnormalities was estimated at 280–560 and 3360–16 800, respectively, and for hypergonadotropic azoospermia 459–918 and 6357–31 785, respectively.
Chromosomal abnormalities in relation to surgical sperm retrieval rate
Data on surgical sperm retrieval were available for 1450 of our 1663 patients (87%). Table I illustrates sperm retrieval rates per chromosomal abnormality category. Sperm retrieval rates were significantly higher in patients with normal karyotypes (60%, 95% CI 57.7–63.1%) compared to patients with abnormal karyotypes (32%, 95% CI 25.9–39.0%, P < 0.001). In Klinefelter syndrome, the most prevalent chromosomal abnormality, the sperm retrieval rate was 28% (95% CI 20.7–35.0%). Moreover, in all azoospermic patients, the sperm retrieval rate was higher in normogonadotropic azoospermia (439/567, 77%, 95% CI 74.0–80.9%) compared to hypergonadotropic azoospermia (382/883, 43%, 95% CI 40.0–46.5%, P < 0.001).
Prevalence of AZF deletions in azoospermia
Data on AZF deletions were available for 1144 of the 1663 patients (69%). Overall, we found an AZF deletion in 6.5% (74/1144, 95% CI 5.0–7.9%) of azoospermic men. An AZF deletion was present in 5.4% (55/1015, 95% CI 4.0–6.8%) of azoospermic men with a normal karyotype and in 14.7% (19/129, 95% CI 8.6–20.8%) of those with an abnormal karyotype (Supplementary Table I). When excluding isolated AZFc deletions (in which spermatogenesis is possible), the prevalences were 1.6% (16/1015, 95% CI 0.8–2.3%) in azoospermic men with a normal karyotype and 13.2% (17/129, 95% CI 7.3–19.0%) in those with an abnormal karyotype.
Discussion
The aim of this study was to evaluate screening for chromosomal abnormalities in non-iatrogenic azoospermia with regard to the clinical consequences that include increased risk for absence of spermatogenesis and prevention of miscarriage or offspring with congenital malformations.
In an unselected cohort of 1663 non-iatrogenic azoospermic men we found a prevalence of chromosomal abnormalities of 14.4% (95% CI 12.7–16.1%) (Table I), which is in agreement with previous reports describing prevalences between 15% and 25% (Vincent et al., 2002; Dul et al., 2012a; Shin et al., 2016; Takeda et al., 2017; Tournaye et al., 2017a). The large size of our cohort enabled us to report separate prevalences of chromosomal abnormalities for hypergonadotropic (20.2%) and normogonadotropic azoospermia (4.9%) (Table I). When counselling couples on the expected results of chromosomal testing, the gonadotropic status of the man may be taken into account as the NNS to identify one chromosomal abnormality in hypergonadotropic azoospermia was 5, in contrast to a NNS of 20 for normogonadotropic azoospermia. However, despite this difference in prevalence of chromosomal abnormalities between these two groups, we found no clinically significant difference between normogonadotropic and hypergonadotropic azoospermia in the NNS to identify an increased risk for absence of spermatogenesis or to prevent miscarriage or offspring with congenital malformations.
In our study, in non-iatrogenic azoospermia, the NNS to prevent one miscarriage or one child with congenital abnormalities was calculated to be 370–739 and 4751–23 757, respectively. We found no clinically significant difference in NNS between men with normogonadotropic and hypergonadotropic azoospermia (Fig. 1). These NNS illustrate that the accuracy of chromosomal screening to prevent miscarriage or offspring with congenital anomalies is limited. Even though confidence intervals for NNS are relatively wide, as we used conservative assumptions not to underestimate the NNS, even the most conservatively estimated NNS suggest limited clinical usefulness. However, given that miscarriage and offspring with congenital malformations are accompanied by significant medical and emotional impact for affected patients as well as financial costs to society, the decision whether or not to perform screening must be considered carefully. Identification of a karyotype abnormality causative for azoospermia can be important in the emotional coping process of the infertile couple. Furthermore, karyotyping of azoospermic patients may identify patients with gonosomal chromosomal abnormalities like Klinefelter syndrome who are at risk for future hypo-androgenism and who may benefit from clinical surveillance as untreated hypo-androgenism may negatively impact bone density, sexual function and psychosocial wellbeing (Lanfranco et al., 2004).
We evaluated whether a tailored approach, including both serum FSH value and testis volume, would result in subgroups of azoospermic men with more precise calculations of the NNS. Both in normogonadotropic and hypergonadotropic azoospermia, inclusion of testis volume resulted in a clinically significantly altered NNS to identify a chromosomal abnormality (NNS in normogonadotropic azoospermia: 11.9 for testis volume <15 ml and 24.6 for testis volume ≥15 ml; NNS in hypergonadotropic azoospermia: 4.3 for testis volume <15 ml and 21.1 for testis volume ≥15 ml). However, inclusion of testis volume did not significantly alter the NNS to prevent a miscarriage or a child with congenital malformations (Supplementary Table III). As clinically estimated testis volume is a less objective measure for testicular function as compared to FSH value, we decided not to include testicular volume as a parameter in our main comparisons. Furthermore, testis volume was not available for all patients, and including these data might have introduced selection bias.
Surgical sperm retrieval is a prerequisite for non-iatrogenic azoospermic men who strive to conceive with their own gametes. In our study, the prevalence of karyotype abnormalities with an increased risk for an AZF deletion associated with absence of spermatogenesis was 1.4% (95% CI 0.8–1.9%). In patients with an AZF deletion associated with absence of spermatogenesis surgical sperm retrieval should not be performed. With karyotyping in azoospermia, the NNS to identify one man with a chromosomal abnormality associated with an increased risk for absence of spermatogenesis was 72. However, by screening for AZF deletions without parallel karyotyping, we found a more favourable NNS of 35 to identify one man with absence of spermatogenesis, with or without an associated karyotype abnormality. Thus, for non-iatrogenic azoospermia, screening for AZF deletions is more accurate than screening for karyotype abnormalities in identifying azoospermic men in whom surgical sperm retrieval should not be performed.
Success rates of surgical sperm retrieval in azoospermic men are known to be compromised. In our study, sperm retrieval rates were significantly higher in patients with normal karyotypes (60%, 95% CI 57.7–63.1%) compared to patients with abnormal karyotypes (32%, 95% CI 25.9–39.0%, P < 0.001), and higher in normogonadotropic azoospermia (77%, 95% CI 74.0–80.9%) compared to hypergonadotropic azoospermia (43%, 95% CI 40.0–46.5%, P < 0.001) (Table I). The sperm retrieval rate in hypergonadotropic patients with a normal karyotype (47%, 95% CI 43–50%) identified in our study is in line with the sperm retrieval rates of 41–44% previously described in patients with non-obstructive azoospermia with a normal karyotype (Vloeberghs et al., 2015; Cissen et al., 2016). In our study, the sperm retrieval rate in Klinefelter syndrome was 28% (95% CI 20.7–35.0%), whereas a recent systematic review and meta-analysis reported a testicular sperm extraction rate of 44% (95% CI 39–48%) (Corona et al., 2017). The relatively low sperm retrieval rate in Klinefelter syndrome in our study may be related to the unselected nature of our study population, although we cannot exclude selection bias as not all patients underwent surgical sperm retrieval. Although both conventional and microTESE were performed, to date there are no prospective data available to state that microTESE yields higher sperm retrieval rates than conventional TESE (Sabbaghian et al., 2014). Moreover, our data on sperm retrieval rate in 151 Klinefelter men is one of the largest datasets on sperm retrieval in Klinefelter syndrome published thus far.
Our study has some weaknesses. Although we studied chromosomal abnormalities in a large cohort of non-iatrogenic azoospermic men, the absolute number of chromosomal abnormalities associated with clinical consequences and adverse pregnancy outcomes in our study was limited, thereby increasing the role of chance. Furthermore, as a retrospective study is the only realistic design to evaluate chromosomal abnormalities in such a large cohort, the intrinsic limitation of selection bias cannot be completely excluded, as not all included patients underwent surgical sperm extraction and data on AZF deletions were only available for part of the patients. Furthermore, selection of relatively ‘more complex’ azoospermic men in our study cannot be completely excluded, as the centre in Brussels served as a tertiary referral centre for Europe. Finally, as there are no large series on outcomes of pregnancies in men with chromosomal abnormalities, our conclusions had to be partly based on assumptions derived from our own data and the literature.
We aimed to evaluate screening for chromosomal abnormalities in an unselected group of non-iatrogenic azoospermic men with regard to clinical consequences and adverse pregnancy outcomes. We found the NNS to identify one man with absence of spermatogenesis in whom surgical sperm retrieval should not be performed to be 72, while screening for AZF deletions is a more accurate means to identify men with absence of spermatogenesis. The NNS to prevent one miscarriage was 370–739 and to prevent one child with congenital malformations was 4751–23 757, and there was no clinically significant difference in NNS between men with normogonadotropic and hypergonadotropic azoospermia. Therefore, we propose that in counselling non-iatrogenic azoospermic men for chromosomal screening, patients should be informed that screening is effective in identifying a karyotype abnormality (in particular in hypergonadotropic azoospermia), while the clinical consequences in terms of prevention of adverse pregnancy outcomes are very limited (in both normogonadotropic and hypergonadotropic azoospermia). For the final decision on chromosomal screening in azoospermia, cost-effectiveness studies need to be done, taking the emotional impact for the couples and financial costs to society of adverse clinical consequences of abnormal karyotypes into account. Our data can be used in modelling cost-effectiveness that will ultimately enable development of evidence-based guidelines on karyotyping in azoospermia.
Supplementary data
Supplementary data are available at Human Reproduction online.
Acknowledgements
The authors thank E. Boven, M. Bensink and G. Knol for their assistance in data collection; T. Dijkhuizen for help with provision of cytogenetic data; and K. McIntyre for editing assistance.
Authors’ roles
J.A.L. and R.B.D. designed the study. R.B.D. collected and analysed the data and wrote the manuscript. V.V. was involved in study design, data collection and data analyses. C.M.A.v.R.-A. performed the cytogenetic interpretation. H.G. performed statistical analyses. C.M.A.v.R.-A. and H.T. were involved in the conception and design of the study. All authors contributed to interpretation of the data and revision of the manuscript. All authors approved the final manuscript.
Funding
No external funding was used for this study.
Conflict of interest
None to declare.
References
Author notes
The authors consider that the first two authors should be regarded as joint first authors.