Table 1 Summary of published studies included

Meng [19]

2013

Asian

PB

PCR-RFLP

rs2234693, rs9340799, rs1256049, rs4986938

Age: 25–38 years (mean age 32.1 ± 5.2 years). Exclusion criteria: abnormal karyotypes, deletions of the Y chromosome, orchitis, varicocele, cryptorchidism, congenital bilateral absence of the vas deferens, hypogonadotropic hypogonadism, and iatrogenic infertility.

TT:83/82, CT:96/126, CC:25/44; AA:151/148, AG:42/89,GG:11/15; GG:103/127, AG:91/102, AA:10/23; GG:155/193, AG:41/48, AA:8/11

0.712, 0.793, 0.699, 0.001

Zalata [5]

2013

Caucasian

PB

PCR-RFLP

rs2234693, rs9340799

Inclusion criteria: same ethnic origin (Caucasians). Exclusion criteria: varicocele, hormonal therapy, hypogonadism, smoking, Y chromosome deletions and karyotype abnormalities. The ages of were not shown in the article.

TT:33/14, CT:32/27, CC:16/19; AA:28/8, AG:36/32, GG: 17/20

0.468, 0.389

Ogata [20]

2012

Asian

PB

PCR-RFLP

rs1256049

Age: 32–52 years (median 41.0 years). Inclusion criteria: no extragenital anomalies, seminal tract obstruction, varicocele, Y chromosomal microdeletion, or retrograde ejaculation; normal karyotypes.

GG:68/64, AG:49/45, AA:8/10

0.604

Bianco [7]

2011

Caucasian

PB

TaqMan assays

rs2234693, rs9340799, rs1256049, rs4986938

Age: 36.1 ± 6.5 years. Exclusion criteria: chromosome anomalies, azoospermia factor (AZF) microdeletions, smoking, alcoholism, occupation, varicocele, and cryptorchidism.

TT:30/37, CT:93/111, CC:64/68; AA:80/100, AG:79/88, GG:20/28; GG:172/201, AG:15/15, AA:0/0; GG:43/28, AG:60/103, AA:84/85

0.468, 0.221, 0.597, 0.712

Safarinejad [21]

2010

Asian

PB

PCR-RFLP

rs2234693, rs9340799, rs1256049, rs4986938

Age: 31.6 ± 4.8 years (range 25–40 years). Inclusion criterion: two years with no reason for their infertility. Exclusion criteria: varicocele or testicular torsion, urinary tract infections, endocrinopathy, karyotype anomalies, Y-chromosome microdeletions, use of drugs, leukocytospermia, a BMI of 30 kg/m2 or greater.

TT:49/33, CT:70/86, CC:45/45; AA:62/41, AG:77/95, GG:25/28; GG:142/152, AG:21/8, AA:1/4; GG:65/80, AG:82/63, AA:17/21

0.486, 0.034, 0.000, 0.132

Lazaros [22]

2010

Caucasian

PB

PCR-RFLP

rs2234693, rs9340799, rs1256049, rs4986938

Age: 33.2 ± 67.5 years. Exclusion criteria: hypogonadotropic hypogonadism, obstructive syndromes of the seminal tract, microdeletions of the Y chromosome, karyotypic abnormalities.

TT:6/20, CT:14/40, CC:9/25; AA:5/13, AG:13/43, GG:11/29; GG:26/80, AG:3/5, AA:0/0; GG:7/17, AG:12/36, AA:10/32

0.609, 0.652, 0.779, 0.246

Khattri [23]

2007

Asian

PB

PCR-RFLP

rs1256049

Age: 23.24 ± 2.06 years. Exclusion criteria: obstruction, endocrinological defect, injuries, karyotypic abnormality, Y-chromosome microdeletions.

GG:397/231, AG:46/21, AA:0/0

0.490

Omrani [24]

2005

Asian

PB

PCR-RFLP

rs1256049, rs4986938

Exclusion criteria: genetic causes of infertility, such as Klinefelter syndrome or Ychromosome microdeletions. The ages of patients were no shown in the article.

GG:103/194, AG:17/9, AA:0/1; GG:51/86, AG:57/88,AA:12/30

0.023, 0.339

Aschim [25]

2005

Caucasian

PB

PCR-RFLP

rs1256049, rs4986938

Exclusion criteria: Klinefelter syndrome or Y-chromosome microdeletions, a history of cryptorchidism were excluded. The ages of patients were no shown in the article.

GG:92/177, AG:14/8, AA:0/1; GG:11/82, AG:48/79, AA:47/25

0.015, 0.394

Kukuvitis [26]

2002

Caucasian

PB

PCR-RFLP

rs2234693, rs9340799

Exclusion criteria: any known aetiologies (varicocele, infections of accessory glands, cryptorchidism, homozygous form of β-thalassemia). The ages of patients were no shown in the article.

TT:38/18, CT:38/25, CC:33/21; AA:30/10, AG:45/28, GG:34/26

0.083, 0.594