High resolution HLA-DRB1 analysis and shared molecular amino acid signature of DRß1 molecules in Occult hepatitis B infection.

AIM: To investigate the association of human leukocyte antigen (HLA)-DRB1 alleles and the variations of polymorphic amino acid changes in DRß1 chain in Shaanxi Han population with Occult hepatitis B infection (OBI). METHODS: High-resolution HLA-DRB1 genotyping was performed in 107 OBI carriers and 280 normal controls. Sequence information was used to assign which amino acids were encoded at all polymorphic positions. Three-dimensional modeling was performed to explore the effect of the key residues on the HLA-DRB1 molecule. RESULTS: Strong susceptible association for allele DRB1*07:01 was observed in OBI carriers. The amino acid variation at HLA-DRß1 molecule revealed susceptible associations for residues Gln4ß, Val57ß(P9), Ser60ß(P9) and Val78ß(P4), the amino acids Arg4ß, Asp57ß(P9), Tyr60ß(P9) and Tyr78ß(P4) showed protective associations. CONCLUSION: Alleles DRB1*07:01 showed strong susceptible associations in OBI carriers. The amino acid variations in DRß molecules revealed significant molecular markers for susceptibility and protection from OBI in Shaanxi Han population.

Human leukocyte antigen class I association with occult hepatitis B virus infection in the Shaanxi Han group: Analysis at the haplotype level.

BACKGROUND: Human leucocyte antigen (HLA) class I genes and haplotypes correlate with hepatitis B virus (HBV) infection. Occult HBV infection (OBI), a special type of chronic HBV infection, is defined as HBV surface antigen negative patients with or those without serologic markers by the means of HBV DNA detection in human plasma or in liver tissue by a diagnostic test. So far, the associations of HLA I haplotypes with OBI have not been reported previously in China. METHODS: A case-control study between 107 OBI subjects and 280 healthy controls from blood donors in the Blood Center of the Shaanxi Province was conducted in the present association analysis. The HLA-A, -B and -C loci of case-control subjects were detected and genotyped by polymerase chain reaction-sequence based typing. The HLA-A, -B and -C haplotypic frequencies were calculated by the maximum likelihood method. RESULTS: The HLA-A*33:03-C*07:01G (pc = 0.039, odds ratio [OR] = 8.996, 95% confidence interval [CI] = 1.825-44.338), B*44:03-C*07:01G (pc = 0.0069, OR = 12.000, 95% CI = 2.507-57.436) and A*33:03-B*44:03-C*07:01G (pc = 0.04, OR = 7.094, 95% CI = 1.387-36.288) haplotypes showed a a significant positive association with OBI. Independent effects demonstrated that HLA-B*44:03 and HLA-C*07:01G gave the main contribution to risk, whereas HLA-A*33:03 was associated only by linkage disequilibrium. CONCLUSIONS: This present study is the first to demonstrate that HLA I haplotypes are associated with OBI in the Shaanxi Han population. The present results suggest that HLA-B*44:03-C*07:01G might be a potential risk factor for OBI. Comparisons of the frequencies of HLA I haplotypes at high resolution were made between OBI from northern Chinese Han and controls. Frequencies of HLA-A-B, A-C, B-C, A-B-C between the OBI group (gray column) and the control group (blank column) were compared. Haplotypes with p < 0.05 in either group were shown. p values for multiple comparisons (pc ) were corrected by Bonferroni correction (*pc  < 0.05).

[Characterization of a rare HLA-C*08:84 allele and analysis of its 3-D molecular structure].

OBJECTIVE: To verify a rare allele of human leukocyte antigen (HLA) and analyze its inheritance and 3D molecular structure. METHODS: PCR-sequence-based typing, PCR-single strand oligonucleotide polymorphism and single allele-specific sequencing were carried out to characterize the rare HLA-C allele and its transmission in the family. Its protein structure was modeled by using SWISS-MODEL, Phyre2 and FATCAT software. RESULTS: Analysis indicated that the rare allele (HLA-C*08:84) has transmitted from the proband's mother and has differed from HLA-C*08:01 by a single base (g.512G>C), resulting in substitution of an amino acid (p.Trp147Ser). Modeling of the 3D structure of the encoded protein indicated that the amino acid residue variation is located at the alpha 2 helix, which participates the formation of pocket F. Modeling of the structures of C*08:84, C*08:01, C*08:02, C*08:03 and C*08:22 has suggested significant variation in the peptide binding regions of the backbone, with root mean square errors being 1.70 nm, 1.79 nm, 0.71 nm and 1.70 nm, respectively. CONCLUSION: A rare HLA-C*08:84 allele has been identified, and its clinical significance has been analyzed.

Prevalence and protective factors of HIV and syphilis infection among men who have sex with men in Northwest China.

BACKGROUND: Men who have sex with men (MSM) continue to be disproportionately impacted by human immunodeficiency virus (HIV) and syphilis in China. Little is known about HIV and syphilis infections among MSM in Xi'an, a developing city in Northwest China. A cross-sectional study with recruitment via snowball sampling was conducted to collect HIV and syphilis infection status and risk factors among MSM in Xi'an between April 2013 to December 2016. Among the 5000 participants, the mean age was 29.0 years (SD 7.7) and the prevalence of HIV, syphilis, and coinfection was 6.5%, 2.2%, and 0.4%, respectively. There was no significant change in HIV prevalence from 2013 to 2016, while the prevalence of syphilis and coinfection showed a downward trend. Multiple logistic regression analyses found that being over 25 years old (OR = 1.647), junior high school/middle school education and below (OR = 3.085), with a sexual role of passive or versatile (OR = 3.300; OR = 2.337), rush poppers use during the last 6 months (OR = 1.660) and syphilis infection (OR = 2.235) were more likely to acquire HIV infection, whereas used condoms in the last episode of anal sex (OR = 0.572) and tested HIV antibody previously (OR = 0.252) were protective factors for HIV infection. HIV prevalence among MSM in Xi'an was stable, whereas the prevalence of syphilis and coinfection showed a downward trend. Interventions to promote HIV and sexually transmitted disease testing and condom use should be strengthened, especially for MSM with low education.

Re-emerging of rabies in Shaanxi province, China, from 2009 to 2015.

To explore the epidemiological, phylogeographic, and migration characteristics of human rabies in Shaanxi province, China from 2009 to 2015. The collected data were described and the sequenced glycoprotein (G) and nucleoprotein (N) genes were implemented to estimate the evolutionary rates and phylogeographic patterns using BEAST v.1.8.2. A total of 269 rabies cases were reported and 70.26% of the cases were male and 61.71% were between the ages of 19-59. The majority of the cases were farmers (83.27%). The estimated evolutionary rate of the N genes was 2.4 × 10-4 substitutions/site/year and the G genes was 3.4 × 10-4 . The time of the most recent common ancestor (TMRCA) was estimated around 1990. We detected viral migration paths from Sichuan, Guizhou, and Hunan to Hanzhong prefecture of Shaanxi and then spreaded to Xi'an and other prefectures. The main population affected by rabies virus was male adult farmers. The evolution rate of rabies viruses in Shaanxi was similar with the prior results reported by others and the ancestor virus should be circulating in neighboring province Sichuan around 1990 and then transmitted to Shaanxi. Promptly standard wound treatment and timely post-exposure prophylaxis should be compulsory for the dog-bitten victims.

LncRNA H19 promotes the differentiation of bovine skeletal muscle satellite cells by suppressing Sirt1/FoxO1.

BACKGROUND: H19 is a well-characterized Long noncoding RNA (lncRNA) that has been proven to promote myoblast differentiation in humans and mice. However, its mechanism of action is still not fully interpreted. METHODS: Using RT-qPCR, we examined H19 RNA levels in various tissues from 1-week, 1-month, 6-month and 36-month old male cattle (i.e., newborn, infant, young and adult). The protein and mRNA levels of MyoG, MyHC, Sirt1 and FoxO1 in the satellite and C2C12 cells with an H19 silencing or overexpression vector were respectively detected using western blot and real-time qPCR. RESULTS: H19 was highly expressed in skeletal muscle at all the studied ages. High expression of H19 was required for the differentiation of bovine satellite cells. Knockdown of H19 caused a remarkable increase in the myoblast-inhibitory genes Sirt1/FoxO1, suggesting that H19 suppresses Sirt1/FoxO1 expression during myogenesis. Western blotting analysis of co-transfection of Sirt1 or FoxO1 expression vectors with pcDNA-H19 indicated that Sirt1/FoxO1 overexpression neutralized the promotion of myoblast differentiation through transfection of pcDNA-H19. CONCLUSION: H19 promoted the differentiation of bovine skeletal muscle satellite cells by suppressing Sirt1/FoxO1.

Relationships between perceived social support and retention among patients in methadone maintenance treatment in mainland China.

The study purpose was to explore relationships between perceived social support and retention in mainland Chinese patients receiving methadone maintenance treatment (MMT). Data collection included baseline information, perceived social support, and retention. A total of 1212 patients completed the cross-sectional survey; 809 (66.7%) perceived good social support and 458 (37.8%) had been re-admitted. Despite controlling baseline information, past retention did not significantly influence perceived social support. At the two-year follow-up, 527 (43.5%) patients terminated MMT. Patients with poorer perceived social support were more likely to terminate treatment, with hazard ratios of 1.31 (95% confidence interval [CI]: 1.10-1.57 without controlling baseline information and past retention) and 1.25 (95% CI: 1.04-1.51 controlling baseline information and past retention). Thus, while MMT retention does not significantly influence perceived social support, good perceived social support is a strong predictor of retention.

Direct Detection of Erythromycin-Resistant Bordetella pertussis in Clinical Specimens by PCR.

Resistance of Bordetella pertussis to erythromycin has been increasingly reported. We developed an allele-specific PCR method for rapid detection of erythromycin-resistant B. pertussis directly from nasopharyngeal (NP) swab samples submitted for diagnostic PCR. Based on the proven association of erythromycin resistance with the A2047G mutation in the 23S rRNA of B. pertussis, four primers, two of which were designed to be specific for either the wild-type or the mutant allele, were used in two different versions of the allele-specific PCR assay. The methods were verified with results obtained by PCR-based sequencing of 16 recent B. pertussis isolates and 100 NP swab samples submitted for diagnostic PCR. The detection limits of the two PCR assays ranged from 10 to 100 fg per reaction for both erythromycin-susceptible and -resistant B. pertussis. Two amplified fragments of each PCR, of 286 and 112 bp, respectively, were obtained from a mutant allele of the isolates and/or NP swab samples containing B. pertussis DNAs. For the wild-type allele, only a 286-bp fragment was visible when the allele-specific PCR assay 1 was performed. No amplification was found when a number of non-Bordetella bacterial pathogens and NP swab samples that did not contain the DNAs of B. pertussis were examined. This assay can serve as an alternative for PCR-based sequencing, especially for local laboratories in resource-poor countries.

Reliability and validity of the multidimensional scale of perceived social support in Chinese mainland patients with methadone maintenance treatment.

INTRODUCTION: The multidimensional scale of perceived social support (MSPSS) is a valid tool for assessing perceived support from family, friends and significant others. However, evidence about reliability and validity of the MSPSS in Chinese mainland patients with methadone maintenance treatment (MMT) is lacking. METHODS: The patients (n=1212) being admitted to the first two largest MMT clinics in Xi'an were recruited in the study. Reliability was estimated with Cronbach's α and intra-class correlation (ICC). Convergent and discriminant validity was assessed using item-subscale correlation. Factorial validity was examined using exploratory and confirmatory factor analysis. The patients answered the questions of MSPSS at baseline and re-test after 6months, respectively. RESULTS: Cronbach's α of the overall MSPSS was 0.92 (subscales range: 0.84-0.89). ICC of the overall MSPSS was 0.65 (subscales range: 0.57-0.64). Better convergent validity (r≥0.40) was demonstrated by the satisfactory hypothesized item-subscale correlation. All of the hypothesized item-subscale correlations were higher than the correlations between the hypothesized items and other subscales, indicating better discriminant validity. Two factors were extracted from the 12 items, with factor 1 mainly covering friends and significant others subscales (explained 55.56% variance) and factor 2 mainly covering family subscale (explained 11.77% variance). In comparison with the proposed three-subscale model, the two-factor observed model did not fit well in this sample according to model fit indices. CONCLUSIONS: The MSPSS has acceptable reliability and convergent/discriminant validity in Chinese mainland MMT patients. The proposed three-factor model of MSPSS is much better fit than the two-factor observed model in this study. Findings of the study will provide evidence of psychometric properties of the MSPSS in MMT patient population and expand the use of the MSPSS in clinical MMT context.

[Survey of Hepatitis B infection and vaccination status among drug users in Xi'an].

OBJECTIVE: To explore seroepidemiological status and vaccine coverage of hepatitis B among drug users in Xi'an. METHODS: 545 drug users in the Xi'an Compulsory Detoxification Center were asked to answer questionnaire and provide blood sample (3-5 ml) for test of HBsAg, anti-HBc and anti-HBs from March to June 2013. Totally, 545 subjects were surveyed and tested. All of them effectively completed the survey. RESULTS: The positive rates of HBsAg, anti-HBc and anti-HBs were 29.4% (160/545), 60.0% (327/545) and 56.1% (306/545), respectively. Eighty five subjects (15.6%) were negative for all of the three markers. The prevalence of HBsAg and anti-HBc among injection drug users were 40.0% (94/235) and 65.6% (154/235), which was significantly higher than non- injection drug users' (21.6% (52/241), 58.5% (141/241)) and mixed non-injection and injection drug users ((20.3% (14/69), 46.4% (32/69)) (χ(2) = 23.518 and 9.017, respectively, P < 0.05) . The HBsAg positive rate (30.6% (153/500)) of subjects with more than once per day of drug using within one year was significantly higher than those who used drugs for 2-3 times per week (15.6% (7/45)) (χ(2) = 4.51, P < 0.05). Only 11.7% (64/545) of drug users had a clear history of hepatitis B vaccination. The vaccination rate of subjects (3.5% (5/141)) with primary education or below was significantly lower than those with high school (16.3% (45/276)) (χ(2) = 26.61, P < 0.05). The vaccination rate of subjects (7.8% (12/153)) over 45 years old was significantly lower than that of subjects below 30 years old (15.9% (21/132)) and 30-44 years old (11.9% (31/260)) (χ(2) = 30.36, P < 0.05). The vaccinees had a significantly higher positive rate of anti-HBs (73.4% (47/64)) than those who without vaccination (53.8% (259/481)) (χ(2) = 8.81, P = 0.003), but the positive rates of HBsAg (16.7% (11/64)) were lower than those who without vaccination (31.0% (149/481)) (χ(2) = 23.52 and 9.02, respectively;P > 0.05). CONCLUSION: The HBV infection status among drug users in Xi'an was in serious condition, while a low vaccination rate was also discovered among them.

Haplotype-dependent HLA-DRB1-DQB1 susceptibility to occult HBV infection in Xi'an Han population.

BACKGROUND: Occult hepatitis B virus (HBV) infection (OBI) is primarily characterized by the persistence of HBV-DNA in the liver tissues and/or in the serum without detectable HBsAg. Human leukocyte antigen (HLA) polymorphisms have been found to be strongly associated with HBV in different ethnic backgrounds. The association of HLA-DRB1-DQB1 haplotypes with OBI has not been previously reported in China. The aim of this study was to identify the potential association of HLA-DRB1-DQB1 haplotypes that may be involved in OBI genetic susceptibility. METHODS: A case-control study was conducted between 107 OBI subjects and 280 healthy controls from the blood donors in the Shaanxi Province Blood Center. The HLA-DRB1, DQB1 loci were genotyped using polymerase chain reaction-sequence based typing (PCR-SBT). Based on the genotype data of the two loci, haplotype estimation was performed. RESULTS: HLA-DRB1*07:01-DQB1*02:02 (pc = 0.344 × 10-3 , OR = 3.489, 95%CI = 2.000-6.088) and HLA-DRB1*09:01-DQB1*03:03 (pc = 0.02, OR = 2.370, 95%CI = 1.450-3.873) serve as the possible risk and susceptibility haplotypes for OBI in Xi'an Han after Bonferroni correction. CONCLUSIONS: This study demonstrated that HLA II haplotypes were significantly associated with OBI in the Xi'an Han population. To the best of our knowledge, this is the first study to associate HLA-DRB1-DQB1 haplotypes with OBI, which can provide valuable insights into the relationship between the various genetic factors and immune responses in the Xi'an population. The findings can also form the basis for future studies about the role of HLA in OBI.

Hantaviruses in rodents and humans, Xi'an, PR China.

Xi'an, the capital of Shaanxi province, located in north-west China, is one of the major endemic areas for haemorrhagic fever with renal syndrome (HFRS). In this study, the epidemiological data of HFRS in Xi'an from 1959 to 2010, especially in the past ten years (2001-2010), were surveyed. The features of hantavirus (HV) host carriers, the molecular characteristics of the HV S gene from hosts and patients, and the genome of the viral isolate were also investigated. Data showed that there might be a ten-year cycle of HFRS in Xi'an. Although the main population group infected over the past ten years was still the 16-59-year-old male farmers, the composition of the population and geographical distribution of HFRS cases have changed slowly, accompanied by the development of environmental and socio-economic situations. Apodemus agrarius remains the dominant host of HV. The HV strains from host rodents and patients in Xi'an belonged to the Hantaan virus (HTNV); no Seoul virus strains were found. Phylogenetic analysis of the small segments of strains taken from hosts and patients, and the whole genome of a viral isolate showed that the virus circulating in Xi'an had high similarity to Guizhou strains. The study also indicated that the vaccine candidate strain A16 isolated during the past century in Xi'an might be a recombinant strain of HTNV and the Amur virus, thus it may not be an optimal vaccine strain.

Identification of a novel allele HLA-C*03:560N by next-generation sequencing in a hematopoietic stem cell recipient.

A frameshift because of a single nucleotide deletion results in a novel null allele, HLA-C*03:560N.

Cohort Profile: The Shaanxi Blood Donor Cohort in China.

Purpose: The Shaanxi Blood Donor Cohort was set up to investigate the impact of blood donation on the health of donors compared with non-blood donors. The specific aims of the study include (1) identifying the geographical and temporal trends of incidence for diseases in both blood donors and non-blood donors; (2) assessing the impact of environmental exposures, lifestyle, body mass index (BMI) and blood type on disease burdens, stratified between blood donors and non-blood donors; and (3) among blood donors, investigating if regular blood donation has a positive impact on donors' health profiles, based on a cohort with a mixed retrospective and prospective study design. Participants: A total of 3.4 million adults, with an equal number and identical demographic characteristics (year of birth, sex and location of residence) of blood donors and non-blood donors, were enrolled on 2012. The one-to-one matching was conducted through a repeated random selection of individuals without any history of blood donation from the Shaanxi Electronic Health Records. The cohort has been so far followed up to the end of 2018, summing to nearly 24 million years of follow-up. The cohort will be followed up prospectively every 3 years until 2030. Findings to Date: Of the 1.7 million blood donors, 418,312 (24.5%) and 332,569 (19.5%) individuals were outpatients and inpatients, accounting for 1,640,483(96.2%) outpatient and 496,061 (29.1%) inpatient visits. Of the same number of non-blood donors, 407,798 (23.9%) and 346,097 (20.3%) individuals were hospital outpatients and inpatients, accounting for 1,655,725 (97.1%) outpatient and 562,337 (33.0%) inpatient visits. The number of outpatient and inpatient visits by non-blood donors was 0.9 and 3.9% higher than those of the blood donors (p < 0.01). Blood donors demonstrate significantly fewer inpatients visits than non-blood donors for major chronic disease categories (p < 0.01). Future Plans: We are currently exploring the long term benefits of blood donation on major chronic disease categories and multimorbidities in this large population cohort. The study results are adjusted by the "healthy donor effect." This cohort study will continue until 2030.

Electroporation is a feasible method to introduce circularized or linearized DNA into B. subtilis chromosome.

Here, we present the electroporation as a feasible and efficient method for introducing circularized and linearized DNA into Bacillus subtilis chromosome. Two integration experiments were carried out and demonstrated the feasibility and efficiency of electroporation to introduce the target DNA into the B. subtilis chromosome. By using of electroporation, a multiple-cistron contained five genes from B. subtilis biotin biosynthetic pathway was introduced into the B. subtilis chromosome efficiently and created a repeated copy in chromosome via a single crossover event. Then an ectopic promoter was introduced conveniently into the upstream of one of the repeated multiple-cistron via a double crossover event. To further demonstrate the application of electroporation in genetic research, the early sporulation gene spo0A of B. subtilis was knocked out and, consequently, the null of sporulation and logged growth was observed in this study. Thus, the electroporation as an alternative method of integration in B. subtilis is feasible and practical.

Association of HLA class II (-DRB1,-DQB1,-DPB1) alleles and haplotypes on susceptibility to aplastic anemia in northern Chinese Han.

The Human Leukocyte Antigen (HLA) genes, playing key roles in mediating the immune response, especially HLA class II alleles were suggested to play a role in the activation of autoreactive T-cells in aplastic anemia (AA). Previous studies in different ethnic groups have indicated that some of HLA-A,-B,-DRB1 alleles had a protective or susceptive association with the prevalence, pathogenesis and development of AA. HLA class II genes, especially HLA-DQB1 and -DPB1 alleles or haplotypes at high-resolution level associated with AA have not been fully identified in northern Chinese Han populations. The aim of this study was to identify association of the variations in HLA class II region with AA in northern Chinese Han population. A recent case-control study, including 96 AA patients and 824 healthy controls was performed. The high-resolution HLA genotyping was conducted by PCR-SBT, -SSO and NGS-ION S5TM platform. Based on genotypic data of the three loci, haplotype estimation was carried out. HLA-DRB1*15:01 (Pc = 2.87 × 10-3; OR = 2.11, 95% CI = 1.45-3.07) and HLA-DQB1*06:02 (Pc = 1.86 × 10-2; OR = 2.01, 95% CI = 1.32-3.06) were the risk and predisposition alleles to AA in northern Chinese Han after considering multiple testing. Moreover, the HLA-DRB1*15:01-DQB1*06:02 (Pc = 4.90 × 10-3; OR = 2.09, 95% CI = 1.37-3.19) and HLA-DRB1*14:05-DQB1*05:03 (Pc = 2.65 × 10-2; OR = 2.82, 95%CI = 1.45-5.50) haplotypes had direct strong relevance to AA and were the susceptible haplotypes. HLA-DPB1 alleles and 23 polymorphic amino acid residues spanning exon 2 ~ 4 of DPß1 molecules have showed no statistically significant associations between AA and controls. The present findings establish a novel link between inherited HLA-DRB1,-DQB1,-DPB1 risk alleles and haplotypes in northern Chinese Han with AA, and open new avenues for development of targeted therapies to prevent or redirect immunopathology in AA.

[An epidemiological survey on saturnism among children due to lead pollution released from township enterprise].

OBJECTIVE: To understand the current situations of saturnism and blood lead levels of children resided in village and circumjacent areas, and to know its relations with sex, age and other factors on children' s health as to providing some evidences for prevention and control. METHODS: An epidemiological survey was conducted for finding out the pollution sources and for a better understanding of the surrounding environment. All 221 children under 14 years old, from the lead pollution villages and surrounding establishments were enrolled, and their blood lead levels were detected by graphite atomizer absorption spectrophotometer method. Symptoms of the saturnism were investigated through a standardized questionnaire. SPSS13.0 software was administrated for data analysis. RESULTS: High blood lead level identification rate was 66.06% (146/221), and saturnism rate 32.13% (71/221). The children's blood lead levels among group 1, group 2, group 3 in this village and jade factory were (161.20 +/- 32.94), (176.60 +/- 43.62), (258.00 +/-106.08) and (238.01 +/- 55.20) microg/L respectively and the significant differences were observed through Kruskal-Wallis test (chi2 = 51.84, df= 3, P<0. 01). The blood lead levels of children from group 3 in this village and the jade factory were higher than those of other two groups. No correlation was found between children's age and blood lead level (r = 0.10, P = 0.13). There was a significant difference in blood lead levels between boys and girls (t' = 3.83, P<0.01). With the children's blood lead levels rising, the occurrence rate of main saturnism symptoms was significantly increased. This survey suggested that the pollution source was a coarse lead smelter. CONCLUSION: The blood lead level should ke overwhelmingly increased among children who live nearby the higher level of lead blood, that living nearby the lead smeltery,might result in stautnism and negative effect on children's healthy.

Medication Adherence in Patients Undergoing Methadone Maintenance Treatment in Xi'an, China.

OBJECTIVES: To identify medication adherence and its influencing factors among patients of 14 methadone maintenance treatment (MMT) clinics in Xi'an, China. METHODS: Data were obtained from the National AIDS Information System-Community Methadone Maintenance Treatment. All patients registered in the system were not permitted to take methadone at home without professionals' supervision. Medication adherence was assessed using categorical (ie, dropout or retained) and continuous (ie, treatment time, methadone use time, and percentage of methadone use days) variables. Percentages of methadone use days of >90%, 50% to 90%, or <50% indicated good, moderate, and poor adherence, respectively. Multivariate Cox stepwise regression analysis was used to identify the influencing factors. RESULTS: Of the 10,398 patients, 52.2% had dropped out of MMT by December 31, 2013, whereas only 11.8% regularly visited the clinic for daily methadone (ie, >90% methadone use days) during a certain period. Protective factors were older age (>30 years); female sex; having no contact with peer drug users over the past month; no needle-sharing experience; a negative initial morphine urine test; and a higher average daily methadone dose (>20 mg) (P < 0.05). Risk factors were answering "others" for marital status; being employed; having a lack of stable income; not living with family; answering "others" for drug use type; frequently engaging in unauthorized drug use during MMT; no readmission; long travel times to the MMT clinic (>30 minutes); having no convenient MMT service time; and being dissatisfied with MMT service (P < 0.05). CONCLUSIONS: Based on our findings, multimodal intervention and management programs can be developed to improve poor medication adherence among the MMT patient population.