Fostering and Conducting Statistical Analysis, Data Mining, and Quantitative Risk Assessments
The Biostatistics and Risk Assessment Center (BRAC) is located in the School of Public Health of the University of Maryland at College Park. Our mission is to foster and conduct statistical analysis, data mining, and quantitative risk assessments in areas of public health and biomedical research.
The primary goal of BRAC is to collaborate with investigators and research institutions in undertaking statistical analysis, bioinformatic procedures, and quantitative risk assessment. Our objectives are:
- To collaborate with investigators and provide help on study design, sample size and power calculations, data collection and data management, statistical modeling, bioinformatic analysis, interpretation of statistical findings, manuscript preparation, and dissemination of results.
- To take the lead on the development of new and improved biostatistical and bioinformatic methods which are needed for cutting-edge multidisciplinary and translational research.
- To develop software tools for new statistical methods developed for the projects.
The Biostatistics and Risk Assessment Center serves as the data center for several research projects. Our data center services include data collection, data management, data storage, and data analysis.
We have a Dell PowerEdge T310 server with an Intel Xeon X3460 Quad-Core Processor and 32GB of RAM Memory. The speed of the processor is 2.8 GHz and has 8MB of cache memory. The server’s hard disk storage capacity is 2 Terabytes (2000 Gigabytes). The data are automatically backed up. The hardware is controlled by a Red Hat Enterprise Linux 5.3 (64 bits) network operating system with an active license. The computer has been working as a web server (Apache Server). We have several database management systems, including MySQL. We will discuss with the investigators their needs and use the most appropriate database management system for their projects.
Current Research Projects
Mei-Ling Ting Lee, Ph.D.:
- Analysis of Genomic, Proteomic, and Sequencing Data
- Threshold Regression Methodology for Cancer Risk Assessment
- Soy Almond Bread as Complementary Therapy for Prostate Cancer
- Statistical Methods for Ophthalmologic and Cluster Data
Shuo Chen, Ph.D.:
- Statistical methods for high-dimensional biomedical data with complex Spatio-temporal structure
- Network and statistical graph models
- Machine learning methods
- Bayesian methods
- Application to neuroimaging, omni-omics, and environmental health data analysis
Raul Cruz-Cano, Ph.D.:
- Canonical Correlation
- Feature Selection and Dimension Reduction Techniques
- Data Analysis
- Statistical Programming
Xin He, Ph.D.:
- Analysis of Recurrent Event Data
- Statistical Models for Panel Count Data
- Penalized Threshold Regression Analysis
- Study on Lubricant Use and Vaginal Microbiome
- Longitudinal Study of the Vaginal Microbiome Prior to Incident STI
- Therapeutic Potential for Aldosterone Inhibition in Duchenne Muscular Dystrophy
- Study on Epidemiology of Concussions in Ivy League/Big Ten Sports
Chengsheng Jiang, Ph.D.:
- Climate Change
- Spatial Statistics
- Air Pollution
- GIS and RS
- Environmental Sampling
Jing Zhang, Ph.D.:
- Network meta-analysis, Generalized evidence synthesis
- Bayesian hierarchical models, Missing data analysis
- Design and analysis of clinical trials
- Machine learning
Shou Chen, Ph.D.
Associate Professor, Epidemiology & Public Health
University of Maryland School of Medicine
Director of Biostatistics and Data Science at the Maryland Psychiatric Research Center
Chengsheng Jiang, Ph.D.
Research Assistant Professor
Maryland Institute of Applied Environmental Health
Yan Li, Ph.D.
Joint Program in Survey Methodology
Jing Zhang, Ph.D.
Department of Epidemiology and Biostatistics
Victor De Gruttola, Ph.D.
Department of Biostatistics
Harvard School of Public Health
Mitchell H. Gail, M.D., Ph.D.
Division of Cancer Epidemiology and Genetics
National Cancer Institute
Robert S. Gold
School of Public Health
University of Maryland
Nick Jewell, Ph.D.
Department of Biostatistics and Statistics
University of California, Berkeley
- LEE M-LT, Gail M, Pfeiffer R, Satten G, Cai T, Gandy A, editors, Risk Assessment and Evaluation of Predictions, (2013). Springer.
- LEE M-LT. Analysis of Microarray Gene Expression Data, (2004), Springer (formerly Kluwer Academic Publishers)
- Mesbah M, Cole BF, LEE M-LT, editors, Statistical Methods for Quality of Life Studies Design, Measurements and Analysis, (2002). Springer (formerly Kluwer Academic Publishers)
- Jewell NP, Kimber AC, LEE M-LT, Whitmore GA , editors, Lifetime Data: Models in Reliability and Survival Analysis, (1996). Springer (formerly Kluwer Academic Publishers)
- Lee, Mei-Ling Ting. Analysis of Microarray Gene Expression Data (2004). Springer.
Peer reviewed articles in the following areas
(Last updated on 12/8/2014)
- Analysis of Genomic Data
- Statistical Models and Applied Probability
- Statistical Models
- Applied Probability
- Applications in Epidemiology, Environmental Studies & Microbiology
- Environmental Research
- Pharmarco Epidemiology
Articles in Analysis of Genomic Data
Chiu CY, Jung J, Chen W, Weeks DE, Ren H, Boehnke M, Amos CI, Liu A, Mills JL, Ting Lee ML, Xiong M, Fan R. Meta-analysis of quantitative pleiotropic traits for next-generation sequencing with multivariate functional linear models. European Journal of Human Genetics 2016 Dec 21 doi: 10.1038/ejhg.2016.170 PMID: 28000696
Guth LM, Ludlow AT, Witkowski S, Marshall MR, Lima LCJ, Venezia AC, Xiao T, Lee M-LT, Spangenburg EE, Roth SM. Sex-specific Effects of Exercise Ancestry on Metabolic, Morphological, and Gene Expression Phenotypes in Multiple Generations of Mouse Offspring, Experimental Physiology, 2013, Vol. 98(10):1469-1484. doi: 10.1113/expphysiol.2012.070300. PMID: 23771910. PMCID: PMC3783594
Cruz-Cano R, Lee M-LT, Leung MY. Logic Minimization and Rule Extraction for Identification of Functional Sites in Molecular Sequences, BioData Mining, 2012, Vol. 5:10. PMID: 22897894. PMCID: PMC3492099
Beyer SJ, Zhang X, Jimenez RE, Lee M-LT, Richardson AL, Huang, Jhiang SM. Microarray analysis of genes associated with cell surface NIS protein levels in breast cancer. BMC Research Notes, 2011, Vol. 4:397-410. doi: 10.1186/1756-0500-4-397, PMID: 21989294. PMCID: PMC3205061
Lee M-LT. Molecular gene-signatures and cancer clinical trials, In: Designs for Clinical Trials: Perspectives on Current Issues. David Harrington, Editor, 2011, 139-155.
Hunter MP, Ismail N, Zhang X, Aguda BD, Lee EJ, Yu L, Xiao T, Schafer J, Lee M-LT, Schmittgen TD, Nana-Sinkam SP, Jarjoura D, Marsh C. Detection of microRNA Expression in Human Peripheral Blood Microvesicles, PLoS ONE, 2008, Vol. 3: 11, e3694. PMID: 19002258. PMCID: PMC2577891
Zhang Y, Bertolino A, Fazio L, Blasi G, Rampino A, Romano R, Lee M-LT, Xiao T, Papp A, Wang D, and Sadée W. Novel polymorphisms in the human dopamine D2 receptor gene affect gene expression, splicing, and neuronal activity during working memory, Proceedings of the National Academy of Sciences, USA, 2007, 104: 20552-20557. PMID: 18077373. PMCID: PMC2154469
Qin S, Qiu W, Ehrlich JR, Ferdinand AS, Richie JP, O?eary MP, Lee M-LT, Liu BC-S. Development of a reverse capture autoantibody microarray for studies of antigen-autoantibody profiling. Proteomics, 2006, 6: 3199-3209. PMID: 16596707
Lee M-LT, Whitmore GA, Bjorkbacka H, Freeman M. Nonparametric Methods for Microarray Data Based on Exchangeability and Borrowed Power. Journal of Biopharmaceutical Statistics, 2005, 15: 783-797. PMID: 16078385
Lee M-LT, Gray RJ, Bjorkbacka H, Freeman MW. Generalized Rank Tests for Replicated Microarray Data. Statistical Applications in Genetics and Molecular Biology, 2005, Vol. 4: No. 1, Article 3. PMID: 16646848
Lee M-LT, Whitmore GA. Intensity-dependent normalization in microarray analysis: a note of concern. Bernoulli, 2004, 10: 943-949.
Lee M-LT, Whitmore GA, Yukhananov RY. Analysis of unbalanced microarray data, Journal of Data Science, 2003; 1: 103-121.
Lee M-LT, Kuo FC, Whitmore GA, Sklar J. Importance of replication in microarray gene expression studies: statistical methods and evidence from repetitive cDNA hybridization. Proceedings of the National Academy of Sciences, 2000; 97: 9834-9839. PMID: 10963655. PMCID: PMC27599
Chen Y, Liu Y, Chu H, Ting Lee ML, Schmid CH (2017). A simple and robust method for multivariate meta-analysis of diagnostic test accuracy. Statistics in Medicine, 2017 Jan 15;36(1):105-121. doi: 10.1002/sim.7093 PMID: 27580758
Hou W-H, Chuang H-Y, Lee M-LT (2016). A threshold regression model to predict return to work after traumatic limb injury. Injury, 2016; 47:483-489. Epub 2015 Dec 2. doi: 10.1016/j.injury.2015.11.032. PMID: 26746983
Xiao T, Whitmore GA, He X, Lee M-LT (2015). The R Package threg to Implement Threshold Regression Model, Journal of Statistical Software, Volume 66, Issue 8. http://www.jstatsoft.org/article/view/v066i0
He X, Chen L, Lei L, Xia HA, Lee MLT (2015) A Simple Method for Estimating Confidence Intervals for Exposure Adjusted Incidence Rate and Its Applications to Clinical Trials. Journal of Biometrics and Biostatistics, Vol. 6: 238. doi:10.4172/2155-6180.1000238
He X, Whitmore GA, Loo GY, Hochberg MC, Lee M-LT. (2015). A model for time to fracture with a shock stream superimposed on progressive degradation: the Study of Osteoporotic Fractures. Statistics in Medicine, Vol.34 (4):652- 663 DOI: 10.1002/sim.6356. PMID: 25376757
Shao F, Li J, Ma S, Lee M-LT (2014). Semi-parametric Varying-coefficient Model for Interval Censored Data with a Cured Proportion. Statistics in Medicine, Vol.33 (10):1700-12. doi: 10.1002/sim.6054. PMID: 24302535
Whitmore GA, Zhang G, Lee M-LT. Constructing normalcy and discrepancy indexes for birth weight and gestational age using a threshold regression mixture model. Biometrics, 2012, 68: 297-306. PMID: 21838731
Xiao T, Whitmore GA, He X, Lee M-LT. Threg: a new command to implement threshold regression model in STATA. The STATA Journal, 2012, 12(2): 257-283.
Li L, Lee M-LT. Analysis of Failure Time Using Threshold Regression with Semi-parametric Varying Coefficients. Statistica Neerlandica, 2011, 65: 164-182.
Lee M-LT, Whitmore GA, Chang M. A Threshold Regression Mixture Model for Assessing Treatment Efficacy in a Multiple Myeloma Clinical Trial. Journal of Biopharmaceutical Statistics, 2008, 18: 1136-1149. PMID: 18991113
Tong X, He X, Sun J, and Lee M-LT. Joint analysis of current status and marker data: an extension of a bivariate threshold model. The International Journal of Biostatistics, 2008, Vol. 4: Iss. 1, Article 21. PMID: 20231913. PMCID: PMC2835457
Lee M-LT, Whitmore GA. Threshold regression for survival analysis: modeling event times by a stochastic process reaching a boundary. Statistical Sciences, 2006, 21: 501-513.
Rosner B, Glynn RJ, Lee M-LT. Extension of the Rank Sum Test for Clustered Data: Two-Group Comparisons with Group Membership Defined at the Subunit Level. Biometrics, 2006, 62: 1251-1259. PMID: 17156300
Lee M-LT, Dehling HG. Generalized two-sample U-statistics for clustered data. Statistica Neerlandica, 2005, 59: 313-323.
Shubina M., Lee M-LT. On maximum attainable correlation for Sarmanov family of bivariate distributions with equal marginal distributions, Communications in Statistics: Theory and Methods, 2004, 33: 1031-1052.
Lee M-LT, Whitmore GA. First Hitting Time Models for Lifetime Data, Handbook of Statistics, Volume 23: Advances in Survival Analysis, edited by N. Balakrishnan and C.R. Rao. Elsevier, North Holland. 2003; 537-543.
Fang HB, Sun J, Lee M-LT, Nonparametric survival comparisons for interval censored continuous data. Statistica Sinica, 2002; 12: 1073-1083.
Lee M-LT, Rosner BA. The average area under correlated ROC curves: a nonparametric approach based on generalized two-sample Wilcoxon statistics. Journal of Royal Statistical Society, series C, Applied Statistics, 2001; 50: 337-344.
Lee M-LT, DeGruttola V, Schoenfeld D. A model for markers and latent health status. Journal of Royal Statistical Society, Series B, 2000; 62: 747-762.
Williamson JM, Lee M-LT. A GEE regression model for the association between an ordinal and a nominal variable. Communications in Statistics: Theory and Methods, 1996; 25:1887-1901.
Lee M-LT. Properties and applications of Sarmonov's family of bivariate distributions. Communications in Statistics: Theory and Methods, 1996; 25:1207-1222.
Cole BF, Lee M-LT, Whitmore GA, Zaslavsky AM. An empirical Bayes model for Markov dependent binary sequences with randomly missing observations. Journal of American Statistical Association, 1995; 90:1364-72.
Lee M-LT. A two state Markov model. Communications in Statistics: Theory and Methods, 1994; 23:615-23.
Benedetti J, Green S, Lee M-LT, Crowley J. Report of the ad hoc committee on design of experiments on double blind refereeing. Statistical Sciences, 1993; 8:318-30.
Lee M-LT, Gross AJ. Lifetime distributions under unknown environments. Journal of Statistical Planning and Inferences, 1991; 29:137-43.
Whitmore GA, Lee M-LT. A multivariate survival distribution generated by inverse Gaussian mixture of exponentials. Technometrics, 1991; 33:39-50.
D'Agostino RB, Lee M-LT, Belanger AJ, Cupples LA, Anderson K, Kannel WB. Relation of pooled logistic regression to time dependent Cox regression analysis: the Framingham Heart Study. Statistics in Medicine, 1990; 9:1501-15. PMID: 2281238
Lee M-LT. A moment test to identify uniformity. Communications in Statistics: Simulation and Computation, 1989; 18 Part B:253-61.
Lee M-LT. Some cross product difference statistics and a test for trends in ordered contingency tables. Statistics and Probability Letters, 1988; 7:41-46.
Block HW, Ting ML. Some concepts of multivariate dependence. Communications in Statistics: Theory and Methods, 1981; A10(8):749-62.
Limnios N, Lee M-LT. Hoeffding's Inequality for Stopped Martingales and Semi-Markov Processes. Communications in Statistics: Theory and Methods, 2005, 34: 713-720.
Lee M-LT, Whitmore GA. Stochastic processes directed by randomized time. Journal of Applied Probability, 1993; 30:302-14.
Lee M-LT, Rachev ST, Samorodnitsky G. Association of stable random variables. Annals of Probability, 1990; 18:1759-64.
Lee M-LT, Gross AJ. Properties of conditionally independent generalized gamma distributions. Probability in the Engineering and Informational Sciences, 1989; 3:289-97.
Lee M-LT. Dependence by reverse regular rule. Annals of Probability, 1985; 13:583-91.
Lee M-LT. Dependence by total positivity. Annals of Probability, 1985; 13:572-82.
Wang HC, Ting ML. Homogeneous Banach spaces of locally integrable functions. Nanta Mathematica 1979; 12:62-70.
Articles in Epidemiology,Pharmarco Epidemiology, Microbiology; Environmental Studies
Lin SC, Lee ML-T, Adirim TA, Transition outcomes for young adults with disabilities, Journal of Pediatric Rehabilitation Medicine: An Interdisciplinary Approach, 2015, Vol. 8:23–30, PMID: 25737345
Beksinska ME, Smit J, Greener R, Todd CS, Lee ML-T, Maphumulo V, Hoffmann V, Acceptability and Performance of the Menstrual Cup in South Africa:A Randomized Crossover Trial Comparing the Menstrual Cup to Tampons or Sanitary Pads, Journal of Women's Health, 2015, Vol.24(2):151-158. PMID: 25682816
He X, Lu X, Chen S, Hochberg MC, Lee M-LT, Association between Obesity, Race and Knee Osteoarthritis: The Multicenter Osteoarthritis Study, International Journal of Statistics in Medical Research, 2014, Vol.3(3):224-230
Hoh JK, Cha KJ, Park MI, Lee M-LT, Park YS. Estimating Time to Full Uterine Cervical Dilation Using Genetic Algorithm, Kaohsiung Journal of Medical Sciences, August 2012; 28(8): 423-428. PMID: 22892163
Rosner B, Glynn RJ, Lee M-LT. A Nonparametric Test for Observational Non-Normally Distributed Ophthalmic Data with Eye-Specific Exposures and Outcomes, Ophthalmic Epidemiology, July 2007; 14(4): 243-250. PMID: 17896304
Finkelstein JS, Lee M-LT, Sowers MF, Ettinger B, Neer RM, Kelsey JL, Cauley JA, Huang MH, Greendale GA. Ethnic variation in bone density in premenopausal and early perimenopausal women: effects of anthropometric and lifestyle factors, Journal of Clinical Endocrinology and Metabolism, 2002; 87: 3057-3067. PMID: 12107201
Finkelstein JS, Sowers MF, Greendale GA, Lee M-LT, Neer RM, Cauley JA, Ettinger B. Ethnic variation in bone turnover in pre- and early perimenopausal women: effects of anthropometric and lifestyle factors. Journal of Clinical Endocrinology and Metabolism, 2002; 87: 3051-3056. PMID: 12107200
Leder BZ, Smith MR, Fallon M, Lee ML, Finkelstein JS. Effects of gonadal steroid suppression on skeletal sensitivity to parathyroid hormone in men. Journal of Clinical Endocrinology and metabolism, 2001; 86: 511-516. PMID: 11158001
Zaleznik DF, Rench MA, Hillier S, Krohn MA, Platt R, Lee M-LT, Flores AE, Ferriri P, Baker CJ. Invasive group B streptococcal disease in pregnant women and neonates from diverse population groups. Clinical Infectious Diseases, 2000; 30:276-281. PMID: 10671328
Platt R, Adelson-Mitty J, Weissman L, Zaleznik D., Lee ML, Baker CJ. Resource utilization associated with initial hospital stays complicated by early-onset group B streptococcal disease. Pediatric Infectious Disease, 1999; 18: 529-533. PMID: 10391183
Lee M-LT, Rosner BA, Weiss ST, Vokonas PS, Gaziano JM. Predictors of cardiovascular deaths: The Normative Aging Study--1963-1998. Clinical Geriatrics, 1999: 7: 77-85.
Fielding JR, Griffiths DJ, Versi E, Mulkern RV, Lee M-LT, Jolesz FA. MR imaging of pelvic floor continence mechanisms in the supine and sitting positions. American Journal of Roentgenology, 1998; 171: 1607-1610. PMID: 9843296
Lee M-LT, Rosner BA, Vokonas PS, Weiss ST. Longitudinal analysis of adult male blood pressure: The Normative Aging Study, 1963-1992. Journal of Epidemiology & Biostatistics, 1996; 1:79-87.
Pasturel BZ, Cruz-Cano R, Rosenberg Goldstein, Palmer A, , Blythe D, Ryan P, Hogan B, Jung C, Joseph SW, Wang MQ, Lee M-LT, Puett R, Sapkota AR. Impact of rurality, broiler operations, and community socioeconomic factors on the risk of campylobacteriosis in Maryland, American Journal of Public Health, 2013, 103(12):2267-75. doi: 10.2105/AJPH.2013.301338, PMID: 24134343
Lee M-LT, Whitmore GA, Laden F, Hart JE, Garshick E. A Case-Control Study Relating Railroad Worker Mortality to Diesel Exhaust Exposure Using a Threshold Regression Model. Journal of Statistical Planning and Inferences, 2009, 139:1633-1642. PMID: 19221608. PMCID: PMC2642623
Tsaih SW, Korrick S, Schwartz J, Lee MLT, Amarasiriwardena C, Aro A, Sparrow D, Hu H. Relation of bone lead and blood lead to renal function among middle-aged and elderly men: the Normative Aging Study. Environmental Health Perspectives. 2004; 112: 1178-82.
Aro A, Amarasiriwardena C, Lee M-LT, Kim R, Hu H. Validation of K x-ray fluorescence bone lead measurements by inductively coupled plasma mass spectrometry in cadaver legs. Medical Physics, 2000; 27: 119-123. PMID: 10659745
Chuang HY, Schwartz J, Hu H, Lee M-LT. Vibration perception thresholds in workers with long-term lead exposure. Occupational and Environmental Medicine, 2000; 57: 588-594. PMID: 10935939. PMCID: PMC1740022
Tsaih SWT, Schwartz J, Lee M-LT, Amarasiriwardena C, Aro A, Sparrow D, Hu H. The independent contribution of bone and erythrocyte lead to urinary lead among middle-aged and elderly man: The Normative Aging Study. Environmental Health Perspectives, 1999; 107, 391-396. PMID: 10210695. PMCID: PMC1566410
Chuang HY, Lee M-LT, Chao KY, Wang JD, Hu H. The relationship of blood lead levels to personal hygiene habits in lead battery workers: Taiwan, 1991-1997. American Journal of Industrial Medicine, 1999; 35: 595-603. PMID: 10332513
Clinton SK, Ahn-Jarvis JH, Grainger EM, Riedl K, Schwartz SJ, Lee ML-T, Cruz-Cano R, Young GS, Lesinski GB, Vodovotz Y. Isoflavone pharmacokinetics and metabolism after consumption of a standardized soy and soy-almond bread in men with asymptomatic prostate cancer. Cancer Prevention Research, Volume 8(11), Pages 1045-1054. August 2015, doi: 10.1158/1940-6207.CAPR-14-0465, PMCID: PMC4633369. PMID: 26276749
Choo PW, Rand CS, Inui TS, Lee M-LT, Canning C, Platt R. A cohort study of possible risk factors for over-reporting of antihypertensive adherence, BioMedical Central Cardiovascular Disorders, 2001; 1: 6. PMID: 11801191. PMCID: PMC64641
Choo PW, Rand CS, Inui TS, Lee M-LT, Canning C, Platt R. A pharmacodynamic assessment of the impact of antihypertensive non-adherence on blood pressure control. Pharmacoepidemiology and Drug Safety, 2000; 9: 557-563. PMID: 11338913
Choo PW, Rand CS, Inui TS, Lee M-LT, Cain E, Cordeiro-Breault M, Canning C, Platt R. Validation of patient reports, automated pharmacy records, and pill counts with electronic monitoring or adherence to antihypertensive therapy. Medical Care, 1999; 37: 846-857. PMID: 10493464
Lee M-LT, Lazarus R. Meta analysis for drug safety data with logistic regressions. Drug Information Journal , 1997; 31: 1189-1193.
Onderdonk AB, Lee M-LT, Liberman E, Delaney ML, Tuomala RE. Quantitative microbiologic models for pre-term delivery, Journal of Clinical Microbiology, 2003, 41: 1073-1079. PMID: 12624032. PMCID: PMC150298
Lee M-LT, Ross RA, Onderdonk AB. Statistical models for vaginal microflora: identifying women at risk for group B streptococcus colonization as a test of concept. Infectious Diseases in Obstetrics and Gynecology. 1997; 5: 336-340. PMID: 18476181
Lee M-LT, Onderdonk AB. Demonstration of subgroups among normal vaginal microflora data. Microbial Ecology in Health & Disease, 1995; 7:107-12.
Lee M-LT, Ross RA, Onderdonk AB. Cluster analysis of vaginal microflora data, Microecology and Therapy 1995; 25:324-328.
Lee M-LT, Ross RA, Delaney ML, Onderdonk AB. Mathematical modelling of the vaginal microflora. Microecology and Therapy 1995; 23:18-21.
Ross RA, Lee M-LT, Delaney ML, Onderdonk AB. Use of continuous culture growth systems for modelling vaginal microflora behaviour. Microecology and Therapy 1995; 23:16-17.
Lee M-LT, Ross RA, Delaney ML, Onderdonk AB. Predicting abnormal microbial population levels in the vaginal ecosystem. Microbial Ecology in Health & Diseases, 1994; 7:235-40.
Ross RA, Lee M-LT, Delaney ML, Onderdonk AB. Mixed-effects models for predicting microbial interactions in the vaginal ecosystem. Journal of Clinical Microbiology, 1994; 32:871-75. PMID: 8027337. PMCID: PMC263155