Meta-Analysis Indicates That the European GWAS-Identified Risk SNP rs1344706 within ZNF804A Is Not Associated with Schizophrenia in Han Chinese Population
et al. (2013) Meta-Analysis Indicates That the European GWAS-Identified Risk SNP rs1344706 within ZNF804A Is Not
Associated with Schizophrenia in Han Chinese Population. PLoS ONE 8(6): e65780. doi:10.1371/journal.pone.0065780
Meta-Analysis Indicates That the European GWAS- Identified Risk SNP rs1344706 within ZNF804A Is Not Associated with Schizophrenia in Han Chinese Population
Ming Li 0
Hui Zhang 0
Xiong-jian Luo 0
Lei Gao 0
Xue-bin Qi 0
Pierre-Antoine Gourraud 0
Bing Su 0
Xiao-Ping Miao, Huazhong University of Science and Technology, China
0 1 State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences , Kunming, Yunnan , People's Republic of China, 2 University of Rochester Flaum Eye Institute, University of Rochester , Rochester , New York, United States of America, 3 Key Laboratory of Mental Health, Institute of Psychology, Chinese Academy of Sciences , Beijing , People's Republic of China, 4 Department of Neurology, School of Medicine, University of California San Francisco , San Francisco , California, United States of America, 5 University of Chinese Academy of Sciences , Beijing , People's Republic of China
Recent genetic association studies have implicated several candidate susceptibility variants for schizophrenia among general populations. Rs1344706, an intronic SNP within ZNF804A, was identified as one of the most compelling candidate risk SNPs for schizophrenia in Europeans through genome-wide association studies (GWASs) and replications as well as large-scale meta-analyses. However, in Han Chinese, the results for rs1344706 are inconsistent, and whether rs1344706 is an authentic risk SNP for schizophrenia in Han Chinese is inconclusive. Here, we conducted a systematic meta-analysis of rs1344706 with schizophrenia in Chinese population by combining all available case-control samples (N = 12), including a total of 8,982 cases and 12,342 controls. The results of our meta-analysis were not able to confirm an association of rs1344706 A-allele with schizophrenia (p = 0.10, odds ratio = 1.06, 95% confidence interval = 0.99-1.13). Such absence of association was further confirmed by the non-superiority test (p = 0.0003), suggesting that rs1344706 is not a risk SNP for schizophrenia in Han Chinese. Detailed examinations of individual samples revealed potential sampling bias in previous replication studies in Han Chinese. The absence of rs1344706 association in Han Chinese suggest a potential genetic heterogeneity in the susceptibility of schizophrenia on this locus and also demonstrate the difficulties in replicating genome-wide association findings of schizophrenia across different ethnic populations.
Funding: This work was supported by grants from the National 973 project of China (grant numbers, 2011CBA00401) and the National Natural Science
Foundation of China (U1202225, 31130051 and 31071101). The funders had no role in study design, data collection and analysis, decision to publish, or
preparation of the manuscript.
Competing Interests: The authors have declared that no competing interests exist.
. These authors contributed equally to this work.
Schizophrenia is one of the most severe complex psychiatric
disorders, and a lifetime prevalence of schizophrenia is estimated
at 0.70% to 1.10% in general populations worldwide . There is
a strong genetic component to these risksthe heritability of
schizophrenia has been estimated to be about 80%  and the risk
of siblings of an affected individual is about eightfold to tenfold
greater than general populations [3,4]. These findings imply that
the application of genetic analyses to schizophrenia seems
plausible and timely.
Schizophrenia is widely acknowledged to be a polygenic
disorder, involving both common variants with low effect size
and rare variants with high effect size , and over the past few
decades efforts in detecting common variants of genetic risks for
schizophrenia have increased. Recent genome-wide association
studies (GWASs) on schizophrenia in populations of European
ancestry have implicated many risk common genetic variants with
small to moderate effect size, including rs1625579 in Chr.1p21.3
region (p = 1.59610211, odds ratio = 1.12) , rs6932590 in
Chr.6p22.1 region (p = 1.4610212, odds ratio = 1.16) , and
rs11819869 in Chr.11p11.2 region (p = 3.8961029, odds
ratio = 1.25) . Among these risk variants achieving genome-wide
level of statistical significance, rs1344706, a SNP located in intron
4 of ZNF804A (Chr.2q32.1), is one of the most compelling
Rs1344706 was firstly identified by a GWAS of a sample from
the UK, in combination with a follow-up replication study among
different world populations , though it did not achieve the
conventional genome-wide significance level. Subsequent
replication studies in Europeans by independent study groups have,
however, demonstrated that rs1344706 is likely an authentic risk
SNP for schizophrenia in Europeans . More importantly, a
recent meta-analysis of a large data set (18,945 cases and 38,675
controls) found genome-wide significant association of rs1344706
with schizophrenia (p = 2.5610211), and the result was more
strengthened when bipolar disorder samples were added into the
meta-analysis (p = 4.1610213) although the effect size is relatively
small (odds ratio = 1.10, 95% confidence interval = 1.071.14)
The significant association of rs1344706 was firstly replicated in
a small Han Chinese sample (566 cases/574 controls from Xian,
China) , suggesting it may also be a risk SNP for schizophrenia
among Chinese. However, other studies on rs1344706 using
different Han Chinese samples yielded inconsistent results. Xiao
et al.  and Chen et al.  observed the association in two
other Han Chinese samples (from Xinxiang and Shandong,
China), but negative results have also been frequently reported.
ODonovan et al.  found that rs1344706 was not significant in
the Han Chinese sample from Shanghai, similar to a study of Han
Chinese samples from Sichuan reported by Steinberg et al. .
Recently, we showed that rs1344706 was not associated with
schizophrenia in two Han Chinese samples from southwestern
China (Yuxi and Kunming, China) , similar to another
Chinese sample from Singapore . Most recently, a large-scale
GWAS (3,750 cases/6,468 controls) in Han Chinese found no
association for rs1344706 in their samples recruited from the
northern, central, and southern parts of China, p = 0.71) .
Overall, whether rs1344706 confers genetic risk of schizophrenia
in Han Chinese or not is still inconclusive.
To test whether rs1344706 is a real risk SNP for schizophrenia
in Chinese population, in the present study we conducted a
comprehensive meta-analysis by combining all available Han
Chinese case-control samples (8,982 cases and 12,342 controls).
Literature Search and Eligible Studies
Using our literature search approaches (a flow chart of the
search process is detailed in Figure 1), a total of nine studies in
Chinese population were identified and included in the
metaanalysis [9,12,1420]. Briefly, there are four replication studies for
rs1344706 in Chinese having one or two samples  that
were included in our meta-analysis. Additionally, there are three
previous meta-analyses of rs1344706 with schizophrenia in world
populations [9,12,18] having Chinese samples independently from
the four replication studies and we extracted the Chinese samples
from these for meta-analysis: a Shanghai sample from ODonovan
et al. , a Sichuan sample from Steinberg et al. , and a
Singapore sample from Li et al. . Furthermore, two
independent Han Chinese GWASs were also included [19,20].
Among these nine studies, a Han Chinese GWAS  has three
independent samples and a replication study  has two
independent samples. Therefore, a total of nine studies with
twelve independent samples were included in our meta-analysis.
The participants in each sample were recruited from local
volunteers and there was no overlap among these studied samples.
Table 1 lists the information of the twelve samples, including
mean age, gender ratio, criteria on definition of schizophrenia,
sample size, etc.
We should note that while some other studies discuss the
connection between ZNF804A and schizophrenia in Han
Chinese, they were not included in our meta-analysis either due
to small sample size, being a case-only study, using samples that
ODonovan, 2008 
Steinberg, 2010 
Shanghai and Anhui 1,224 36.2612.4
Beijing and Shandong 1,510 36.969.3
2,788 60.9612.2 35.5
2,010 56.1613.5 47.7
*see below 57.3
overlap with those already included in our meta-analysis, or where
data was not available from the authors of these studies. The list of
these studies is shown in Table S1.
Among these twelve independent case-control samples, three of
them reported significant association of rs1344706 with
schizophrenia in Chinese , while the other nine did not [9,12,17
20]. To test if rs1344706 is an authentic risk SNP for
schizophrenia in Chinese, we performed a series of analyses, and
discussed the reasons for this inconsistency.
Assessment of Publication Bias
STATA 11.0 software (Stata Corp LP, College Station, Texas,
United States) was used to detect the presence of potential
publication bias. Beggs funnel plot (Figure 2) for meta-analysis of
rs1344706 seems symmetrical (Beggs p = 0.63), suggesting no
evidence of publication bias. Eggers regression test also showed no
evidence of publication bias (p = 0.14, 95%CI = [21.16, 7.07]).
Regression Analyses on Potential Influential Factors
We extracted the data for mean age and gender ratio from each
study (Table 1), and then calculated the allelic-specific odds ratios
for rs1344706 using allele counts in cases and controls for each
study (Table 2). Afterward, we performed regression analyses to
test if these two factors could influence the odds ratios. Since data
of mean age was not available in the study by Steinberg et al. ,
their sample from Sichuan was not included in this analysis.
Regression analyses showed that the odds ratios for rs1344706
were not influenced by mean age in patients with schizophrenia
(p = 0.16) or in healthy controls (p = 0.12), and the odds ratios were
also not influenced by the gender ratio among schizophrenia
patients (p = 0.48) or healthy subjects (p = 0.35).
To further test if the inconsistent association of rs1344706 in
Chinese was caused by other factors, e.g. geography, we first
ascertained the sample collection area of each study according to
information provided in their published papers and categorized
these area into Northern, Central and Southern China, and
conducted regression analysis with the odds ratios. The result was
not significant (p = 0.47). Furthermore, we obtained the latitude of
each sample collection area and tested their associations with the
odds ratios for rs1344706, and still no significant associations were
observed (p = 0.40).
Before performing the meta-analysis, we conducted a power
analysis (Figure S1A) on our total sample size using the
following assumptions: 8,982 patients with schizophrenia and
12,342 controls, two-tailed a = 0.05, and the frequency of A-allele
in Chinese (0.5206). Given the inconsistent odds ratios of
rs1344706 for schizophrenia in Han Chinese, we used two
commonly observed odds ratios in genetic association studies, 1.10
and 1.20. The present sample size revealed a .92% power of
detecting a significant association of allele given an odds ratio of
1.10 (corresponding to a weak gene effect). When an odds ratio
of 1.20 was assumed, i.e. a weak to moderate gene effect, our
sample size showed .99% power to detect significance (a,0.05).
Meta-analysis of rs1344706 with Schizophrenia
Overall, we recruited a total sample size of 21,324 subjects for
meta-analysis, including 8,982 cases and 12,342 controls. The
analysis of the allelic association of the A-allele with the risk of
schizophrenia revealed significant heterogeneity among the twelve
individual samples (x2 = 29.23, df = 11, p = 0.002), and
metaanalysis (Z-score test) of the combined samples was assessed with
the random-effect model. By combining the twelve samples in the
meta-analysis, we found that rs1344706 was not associated with
schizophrenia (Z = 1.62, p = 0.10, odds ratio = 1.06, Table 2).
The forest plot of the meta-analysis is presented in Figure 3.
Figure 2. Beggs funnel plot with pseudo 95% confidence limits for meta-analysis of rs1344706.
A detailed examination of the association results of rs1344706 in
Han Chinese samples indicated that the Xian sample  showed
the lowest p-value (p = 0.00083), but the frequency of A-allele in
their control sample is 0.457 (highlighted in Table 2), highly
different from studies in other Chinese control samples (shown in
Table 2) as well as the Han Chinese data from the
1000-HumanGenome (the A allele frequency is 0.5206). This striking
difference can hardly be explained by currently known genetic
divergence between southern and northern Chinese populations
, because no significant difference was observed among the
other Chinese samples, suggesting the possibility of a biased
sampling of the control sample in the Xian study  that
subsequently led to a false positive result. Hence, whether the data
N Cases/N Controls
ODonovan, 2008 
Steinberg, 2010 
All Chinese samples
Shanghai and Anhui
Beijing and Shandong
Guangdong and Guangxi
OR, odds ratio; CI, confidence interval.
Test of heterogeneity: x2 = 29.23, df = 11, p = 0.002.
I2 (variation in OR attributable to heterogeneity) = 62.4%.
The result for the combined samples (p = 0.10, Z = 1.62) was assessed using the Mantel-Haenszel method with the random-effects model.
The frequency of A-allele in the Xian control sample is highlighted in gray.
Figure 3. Forest plot of meta-analysis for rs1344706 [A] in Chinese sample. OR is the odds ratio for each individual sample. Overall
refers to the combined sample.
from the Xian sample should be considered as an authentic result
for rs1344706 is questionable.
Although Xiao et al.  and Chen et al.  also reported
significant associations of rs1344706 with schizophrenia, their
samples were much smaller as compared with the other Chinese
samples, and their results may not be very representative.
Leave-one-out sensitivity analysis to determine whether the
meta-analysis results were driven by any sample data and therefore
suggestive of a winners curse phenomenon  revealed that
removal of any of the included samples still led to the
nonsignificant (or marginal significant) association of rs1344706 with
schizophrenia using the eleven remaining samples (Table S2).
Furthermore, we noticed that when the Xian sample was
removed from the meta-analysis, the estimates of the p-value for
the heterogeneity test increased from 0.002 to 0.03, suggesting that
the genetic heterogeneity was mainly caused by the Xian sample,
and when the Xian sample was removed from the meta-analysis,
the p-value remained non-significant (Z = 1.13, p = 0.26, odds
ratio = 1.03, Table S2).
Equivalence-based Analysis to Test the Absence of
Association between rs1344706 and Risk of
Non-superiority test was conducted to confirm the absence of
association between rs1344706 and schizophrenia in Chinese. The
null hypothesis is that the frequency of A-allele at rs1344706 in
schizophrenia patients is greater by 3% than that in controls. The
3% was set based on the reported differences of rs1344706 A-allele
between schizophrenia patients and healthy controls in the
discovery UK GWAS  and the first European replication study
 as well as the first Chinese replication study , i.e. 7.0%,
4.0% and 7.0% respectively. Thus, a 3% excess in cases can be
regarded as a the lower bound of previous estimations, which
would correspond to an odds ratio of 1.12 according to the allele
distribution of rs1344706 in Han Chinese.
The non-superiority p-values are presented Table 3. Overall,
the result of the combined Chinese case-control samples supports
the absence of association (p = 0.0003), suggesting that the excess
of rs1344706 A-allele in the cases is lower than 3% (i.e. odds
ratio,1.12), which support the absence of association between
rs1344706 and schizophrenia in Han Chinese.
Recently, ODonovan et al. undertook a GWAS with 479 UK
schizophrenia cases and 2,937 controls in tandem with a follow-up
replication study of 16,726 additional subjects, and found that
rs1344706 in ZNF804A is significantly associated with
schizophrenia . Subsequently, the association of rs1344706 with
schizophrenia was consistently reported by the Irish Case/Control
study of schizophrenia (ICCSS) , the International
Schizophrenia Consortium (ISC) , the Molecular Genetics of
Schizophrenia (MGS)  and then in a large-scale meta-analysis
of independent samples including mainly European subjects .
A further meta-analysis of rs1344706 in 18,945 schizophrenia
patients and 38,675 controls supported this association between
rs1344706 and schizophrenia (p = 2.5610211), though again, the
sample mostly consisted of European subjects . These data
strongly indicated that rs1344706 is a promising risk SNP for
schizophrenia in European populations, but as we pointed out
earlier the association is less clear among other populations,
notably Han Chinese.
We conducted a meta-analysis combining all available Han
Chinese case-control samples to test this association in a
nonEuropean population and found that rs1344706 was not associated
with schizophrenia in the combined samples, and the effect size of
rs1344706 for schizophrenia was smaller in Chinese than in
Europeans (odds ratio for A-allele, 1.06 in Chinese vs. 1.12 in
Europeans) . This was not surprising, considering that
rs1344706 is a genome-wide significant risk SNP for schizophrenia
ODonovan, 2008 
Steinberg, 2010 
All Chinese samples
Shanghai and Anhui
Beijing and Shandong
Delta of A-allele
carrier frequency (%)
Nonsuperiority P-value H0: A
frequency, cases.controls +3%
For each of the samples, a non-superiority p-value is reported that corresponds to the statistical significance of the null hypothesis that the frequency of the rs1344706
A-allele is greater in schizophrenia cases than in controls and differs by at least 3%.
in Europeans [9,13]. We then compared our effect size with the
independent replication studies in Europeans, and found that the
effect size in our analysis was still smaller than the results reported
by the ICCSS (odds ratio = 1.20, p = 0.0113) , the ISC (odds
ratio = 1.08, p = 0.029) , and the MGS samples (odds
ratio = 1.09, p = 0.0262) . The differences of rs1344706 in
association with schizophrenia between Europeans and Han
Chinese likely then reflects the genetic heterogeneity often
observed in the genetic association analyses for complex diseases,
probably as a result of differential population histories. Other
population specific factors, such as diet, culture, or environmental
exposure may also contribute to this observed heterogeneity.
We further compared the sample size between our
metaanalysis (case/control, 8,982/12,342) and the studies in
Europeans, and found that our total sample size was larger than the
discovery GWA+replication studies on rs1344706 in ODonovan
et al. (7,308/12,834, p = 1.6161027) , but smaller than the
meta-analysis in Steinberg et al. (5,077/20,506, p = 0.0029) .
The power of our sample, however, was larger (97.6%) than those
two samples (96.1% and 93.5%, respectively) under the same
assumption on the reported OR of 1.12 in Europeans  and the
risk allele (A) frequency of 0.6235 in healthy European populations
(Figure S1B). In addition, our sample size was much larger than
the samples from ICCSS (1,021/626) , ISC (2,519/2,110) 
and MGS (3,967/3,624)  (Figure S1C), in which all three
found significant associations for rs1344706 whereas we did not.
These comparisons further suggest that the non-significant
association for rs1344706 in our meta-analysis was not caused
by the sample size, but is likely due to the relatively small effect size
of this SNP in Han Chinese.
We have demonstrated that our sample has enough power to
detect significance using the odds ratios corresponding to small
effect size (odds ratio = 1.10) and small-to-moderate effect size
(odds ratio = 1.20). However, if we use the observed odds ratio
(1.06) in Chinese, the present sample size only showed 55.4%
power of detecting significant association. Alternatively, given the
observed odds ratio (1.06) is authentic, the sample size would have
to be increased to more than 24,786 cases and 24,786 controls in
order for the sample to have a .90% power of detecting a
significant association (a,0.05). Based on these assumptions,
studies on rs1344706 in small Chinese case-control samples are
unlikely to observe significant results. That said, there are three
previous studies reporting significant associations of rs1344706 in
small samples  with large effect sizes (1.25#odds
ratio#1.32), almost achieving the effect size of genome-wide scan
in UK samples (odds ratio = 1.38). This is inconceivable given the
notion of the winners curse, that we would expect a much smaller
effect size in replication studies as compared with the discovery
GWASs. Accordingly it is difficult to judge whether the reported
positive results were real or caused by chance.
In the meta-analysis of the twelve Chinese case-control samples,
it should be noted that we did not perform population stratification
analysis in the combined samples. However, among these twelve
individual samples, there is no obvious population stratification in
the Shanghai , Taiwan , Yuxi and Kunming  samples
which were reported in previous studies. There is also no
population stratification in Singapore sample (l = 1.012)
calculated using genome-wide SNPs (Illumina 1M array). Additionally, the
Shanghai and Anhui, Beijing and Shandong, and Guangdong and
Guangxi samples were merged as the primary GWAS samples in
the GWAS of Shi et al. , and there was no population
stratification in these samples. The four remaining samples from
Sichuan, Xian, Xinxiang, and Shandong have not been tested for
population stratification, and notably, three of these show
significant association for rs1344706 (Xian, Xinxiang and
Shandong) . Consequently, we cannot exclude the
possibility that the positive results in these three samples were
caused by potential population stratification.
The data presented in our analysis is limited, and consequently
we are cautious in the interpretation of our results or making any
definitive conclusions. In this study, we only tested rs1344706, and
the other SNPs in ZNF804A were not studied in most of the
analyzed Chinese samples. However, in a previous study, we
performed a relatively systematic analysis of the ZNF804A region
(up to 111 SNPs) in several Han Chinese samples (Singapore,
Yuxi, Shanghai and Anhui, Beijing and Shandong, and
Guangdong and Guangxi), which we did include in the present study and
found that most of the common SNPs in ZNF804A were not
associated with schizophrenia in Chinese populations .
Through our meta-analysis of all the available Han Chinese
case-control samples, we did not find evidence for association of
rs1344706 with schizophrenia. This is not unexpected, given that
the effect size of rs1344706 to schizophrenia risk in Chinese is
smaller than that found in Europeans. Moreover, because a
nonsignificant difference test cannot be interpreted as acceptance of
the null hypothesis, the equivalence-based method that provides
the possibility of observing a lack of association by chance was
conducted to avoid the false-negative results in this study. The
pvalue of the non-superiority test for rs1344706 is 0.0003 in the
combined Chinese samples, supporting the absence of association
between rs1344706 and schizophrenia. Interestingly, rs1344706 is
not the only SNP showing large differences in associations with
schizophrenia between Han Chinese and Europeans, and similar
situations were also observed for some other GWAS-identified
SNPs in Europeans including NRGN rs12807809, RELN
rs7341475, and CNNM2 rs7914558 [6,7,26], all of which were
reported to be not significant in Chinese [25,27,28].
Collectively, the current data to date does not support
speculations that rs1344706 is a risk SNP for schizophrenia in
Chinese, and the failures of replicating rs1344706 in the present
sample suggest a potential genetic heterogeneity of schizophrenia
susceptibility on this locus, likely resulting from large differences in
linkage disequilibrium patterns of this genomic region covering
rs1344706 between European and Han Chinese, as demonstrated
in our previous study . Moreover, for schizophrenia and other
mental disorders, there is marked phenotypic heterogeneity of
clinical symptoms , which could confound genetic association
results between different ethnic populations. Consequently, the
present study invites to be careful in inferring replication results of
complex psychiatric disorders, such as schizophrenia, across
different ethnic populations.
Materials and Methods
Systematic Literature Search
The research protocol was approved by the internal review
board of Kunming Institute of Zoology, Chinese Academy of
Sciences. We firstly considered all the studies listed for ZNF804A
on the SZGene database  and also searched PubMed with the
search terms ZNF804A and schizophrenia as well as
schizophrenia and GWAS. Once the articles had been collected, their
bibliographies were then searched for additional references.
Studies published before January 19, 2013 were considered in
this analysis. We read all the relevant papers to see if the studies
used Chinese samples. After this preliminary literature search,
eighteen non-duplicate studies were identified, including thirteen
candidate gene studies using Chinese samples and five GWASs in
Han Chinese. Whether they were then to be included in the
metaanalysis was determined according to further inclusion criteria as
the following section describes.
Selection of Studies for Inclusion
Eligible studies in the meta-analysis must meet the following
criteria: (1) be case-control studies, case-only and family-based
studies were excluded; (2) contain at least 100 cases and 100
controls; (3) case status being defined as having diagnosis of
schizophrenia according to the DSM-IV or ICD-10 criterion
assessed by established psychiatric interviews, with control subjects
having no history of mental disorder, other neurological disorder,
alcohol dependence, or drug dependence; (4) studies where the
samples have no overlap with the other identified studies; (5)
rs1344706 was genotyped and in Hardy-Weinberg equilibrium in
healthy controls (p.0.05).
For each candidate gene study, the following data was
extracted: (1) author(s) and year of publication; (2) methods,
including study design, sample size, sample collection area,
definition of case status, and genotyping method; (3) sample
characteristics, i.e., gender ratio and mean age; and (4) data for
rs1344706 (allele counts). All the required data were available in
the published studies or from supplementary information, except
for one study that contained no information on the mean age and
genotyping method .
For the GWASs, we recruited the following data: (1) author(s)
and year of publication; (2) methods; and (3) sample
characteristics. However, if rs1344706 was not available from the main text
or supplementary information of these GWASs, we contacted the
corresponding authors to request access to the data. The authors
of two GWASs provided the data for rs1344706 [19,20], but the
author of another GWAS did not reply to our requests , and
was accordingly excluded from further analysis.
Data from each study was extracted independently by two
investigators (ML and HZ), using a standardized data extraction
form. In cases of disagreement of study inclusion, a third
investigator was involved (XJL). Disagreement over eligibility of
a study was resolved by discussion until a consensus was reached.
Publication bias was assessed visually using a funnel plot and
tested with Eggers regression test  as well as the Beggs test,
which is based on Kendalls-t , with p,0.10 being considered
A random effects regression of odds ratio with mean age and the
proportion of males as covariates was performed with the use of
SPSS 16.0 (SPSS inc, Chicago, IL, USA) to determine whether
these covariates could influence odds ratios for rs1344706. We also
analyzed whether the sample collection area could impact the
observation of odds ratios.
Power analysis was performed by the Power and Sample Size
Program software , and the commonly observed odds ratio of
1.10 and 1.20 were applied in the power analysis, which
correspond to a weak gene effect and a weak to moderate
gene effect, respectively.
Meta-analysis examined the allelic association of the rs1344706
A-allele with the risk of schizophrenia relative to the C-allele (odds
ratio for A-allele). Allele frequencies and counts were extracted for
cases and controls. For some studies, allele frequencies and counts
were calculated from the available data .
To combine the individual studies, we conducted meta-analyses
using Review Manager 4.2.2 (http://ims.cochrane.org/revman/
download/revman-4). The heterogeneity between individual
studies was tested using the Cochrans (Q) x2 test, which is a
weighted sum of the squares of the deviations of individual odds
ratio estimates from the overall estimate. When the odds ratios are
homogeneous, Q follows a x2 distribution with degrees of freedom.
If PQ ,0.10, the heterogeneity is considered statistically
significant. Inconsistency across studies was quantified with the
I2 metric (I2 = Q-d.f./Q), which can be interpreted as the
percentage of total variation across several studies due to
heterogeneity. I2 takes values between 0 and 100%, with higher
values denoting a greater degree of heterogeneity (025%: no
PRISMA Flow Chart.
heterogeneity; 2550%: moderate heterogeneity; 5075%: large
heterogeneity and 75100%: extreme heterogeneity). In the
presence of heterogeneity among individual studies, we used
random-effects models to combine the sample and to calculate the
odds ratio and the corresponding 95% confidence interval (CI);
otherwise, a fixed-effect mode was used. We used a forest plot to
graphically present the pooled odds ratios and the 95% CIs. Each
study was represented by a square in the plot, and the weight of
each study was also shown. P,0.05 was considered statistically
Sensitivity analysis was conducted to assess the potential
influences of any one single study on the pooled odds ratios.
Within each meta-analysis, included studies were removed one at
a time to check for significant alterations to pooled odds ratios and
The non-superiority test was conducted to confirm the absence
of association between rs1344706 and schizophrenia, and this
equivalence-based analysis were performed with STATA 11.0
(Stata Corp LP, College Station, Texas, United States), using the
command equip. Detailed descriptions of the nonsuperiority test
can be found in previous studies [35,36].
Power analysis for the studied samples.
Table S1 Studies referring ZNF804A and schizophrenia
in Han Chinese, but not meet the inclusion criteria for
Leave-one-out sensitivity analysis for
metaConceived and designed the experiments: ML BS. Performed the
experiments: ML HZ XJL. Analyzed the data: ML BS. Contributed
reagents/materials/analysis tools: XBQ LG PAG. Wrote the paper: ML
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