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Power of a randomization test in a single case multiple baseline AB design
A randomization test can be used to statistically test hypotheses in multiple baseline designs to complement the commonly used visual inspection analysis. A crossed factor simulation study was performed to investigate the power of a randomization test in an multiple baseline design. The results show that the degree of autocorrelation of the observations, the number of participants, the effect size, the overlap of possible start moments of the intervention between participants, the ratio of the number of measurements in the baseline- and intervention phase, a gradually emerging effect, and the number of measurements had strong main effects on the power. The two-way interactions between number of participants and effect size, and between the number of measurements and the number of start moments of the intervention also had a large effect. An online tool was developed to calculate the power of a multiple baseline design given several design characteristics.
Journal Article
Two kisses for Maddy : a memoir of loss & love
The author's memoir recounting his wife Liz's death shortly after the birth of their daughter Madeline and how he and his daughter Maddy have built a life for themselves--grounded in large part in the life and marriage he shared with Liz.
Book
Systematic Use of Visual Analysis for Assessing Outcomes in Single Case Design Studies
Single case designs (SCDs) allow researchers to objectively evaluate the impact of an intervention by repeatedly measuring a dependent variable across baseline and intervention conditions. Rooted in baseline logic, SCDs evaluate change over time, with each participant serving as his or her own control during the course of a study. Formative and summative evaluation of data is critical to determining causal relations. Visual analysis involves evaluation of level, trend, variability, consistency, overlap, and immediacy of effects within (baseline and intervention) and between conditions (baseline to intervention). The purpose of this paper is to highlight the process for visually analysing data collected in the context of a SCD and to provide structures and procedures for evaluating the six data characteristics of interest. A checklist with dichotomous responses (i.e., yes/no) is presented to facilitate implementation and reporting of systematic visual analysis.
Journal Article
Testing delayed, gradual, and temporary treatment effects in randomized single-case experiments: A general response function framework
Randomization tests represent a class of significance tests to assess the statistical significance of treatment effects in randomized single-case experiments. Most applications of single-case randomization tests concern simple treatment effects: immediate, abrupt, and permanent changes in the level of the outcome variable. However, researchers are confronted with delayed, gradual, and temporary treatment effects; in general, with “response functions” that are markedly different from single-step functions. We here introduce a general framework that allows specifying a test statistic for a randomization test based on predicted response functions that is sensitive to a wide variety of data patterns beyond immediate and sustained changes in level: different latencies (degrees of delay) of effect, abrupt versus gradual effects, and different durations of the effect (permanent or temporary). There may be reasonable expectations regarding the kind of effect (abrupt or gradual), entailing a different focal data feature (e.g., level or slope). However, the exact amount of latency and the exact duration of a temporary effect may not be known a priori, justifying an exploratory approach studying the effect of specifying different latencies or delayed effects and different durations for temporary effects. We provide illustrations of the proposal with real data, and we present a user-friendly freely available web application implementing it.
Journal Article
Model selection of GLMMs in the analysis of count data in single-case studies: A Monte Carlo simulation
Generalized linear mixed models (GLMMs) have great potential to deal with count data in single-case experimental designs (SCEDs). However, applied researchers have faced challenges in making various statistical decisions when using such advanced statistical techniques in their own research. This study focused on a critical issue by investigating the selection of an appropriate distribution to handle different types of count data in SCEDs due to overdispersion and/or zero-inflation. To achieve this, I proposed two model selection frameworks, one based on calculating information criteria (AIC and BIC) and another based on utilizing a multistage-model selection procedure. Four data scenarios were simulated including Poisson, negative binominal (NB), zero-inflated Poisson (ZIP), and zero-inflated negative binomial (ZINB). The same set of models (i.e., Poisson, NB, ZIP, and ZINB) were fitted for each scenario. In the simulation, I evaluated 10 model selection strategies within the two frameworks by assessing the model selection bias and its consequences on the accuracy of the treatment effect estimates and inferential statistics. Based on the simulation results and previous work, I provide recommendations regarding which model selection methods should be adopted in different scenarios. The implications, limitations, and future research directions are also discussed.
Journal Article
Cerebrovascular Disease in Patients with COVID-19: A Review of the Literature and Case Series
COVID-19 has been associated with a hypercoagulable state causing cardiovascular and neurovascular complications. To further characterize cerebrovascular disease (CVD) in COVID-19, we review the current literature of published cases and additionally report the clinical presentation, laboratory and diagnostic testing results of 12 cases with COVID-19 infection and concurrent CVD from two academic medical centers in Houston, TX, USA, between March 1 and May 10, 2020. To date, there are 12 case studies reporting 47 cases of CVD in COVID-19. However, only 4 small case series have described the clinical and laboratory findings in patients with COVID-19 and concurrent stroke. Viral neurotropism, endothelial dysfunction, coagulopathy and inflammation are plausible proposed mechanisms of CVD in COVID-19 patients. In our case series of 12 patients, 10 patients had an ischemic stroke, of which 1 suffered hemorrhagic transformation and two had intracerebral hemorrhage. Etiology was determined to be embolic without a clear cause identified in 6 ischemic stroke patients, while the remaining had an identifiable source of stroke. The majority of the patients had elevated inflammatory markers such as D-dimer and interleukin-6. In patients with embolic stroke of unclear etiology, COVID-19 may have played a direct or indirect role in the processes that eventually led to the strokes while in the remaining cases, it is unclear if infection contributed partially or was an incidental finding.
Journal Article
Applied hybrid single-case experiments published between 2016 and 2020: A systematic review
Single-case experimental designs (SCEDs) are frequently used research designs in psychology, (special) education, and related fields. Hybrid designs are formed by combining two or more of the basic SCED forms (i.e. phase designs, alternation designs, multiple baseline designs, and changing criterion designs). Hybrid designs have the potential to tackle complex research questions and increase internal validity, but relatively little is known about their use in actual research practice. Therefore, we systematically reviewed SCED hybrid designs published between 2016 and 2020. The systematic review of 67 studies indicates that a hybrid of phase designs and multiple baseline designs is most popular. Hybrid designs are most frequently analyzed by means of visual analysis paired with descriptive statistics. Randomization in the study design is common only for one particular kind of hybrid design. Examples of hybrid studies reveal that these designs are particularly popular in educational research. We compare some of the results of the systematic review to those obtained by Hammond and Gast, Shadish and Sullivan, and Tanious and Onghena. Finally, we discuss the results of the present systematic review in light of the need for specific guidelines for hybrid designs, including analytical methods, design specific randomization and reporting, and the need for terminological clarification.
Journal Article
Adalimumab and Tofacitinib Combination Therapy for Pyoderma Gangrenosum: A case report
Introduction: Pyoderma gangrenosum (PG) is a rare inflammatory skin disease causing progressive necrotizing ulcers with limited treatment options due to adverse effects and high recurrence rates. Case Presentation: We present a case of a 70-year-old elderly patient diagnosed as PG, which was unresponsive to initial prednisolone treatment. After approximately three weeks of an individualized treatment regimen of adalimumab combined with tofacitinib, disease progression was halted, accompanied by a significant reduction in ulcer size, reduced exudation, and substantial pain relief. Subsequent tapering and discontinuation of prednisolone, followed by six weeks of combined adalimumab and tofacitinib and eight weeks of tofacitinib monotherapy, resulted in complete ulcer healing by week 17. No recurrence of inflammatory activity was observed during the follow-up period of over 7 months.
Journal Article
Stevens-Johnson Syndrome Following A single Ampicillin Dose in an Elderly Patient: A Case Report
Stevens-Johnson Syndrome (SJS) is a rare but life-threatening mucocutaneous disorder, most commonly triggered by medications. This case report presents a 75-year-old Armenian female who developed severe SJS following a single dose of ampicillin. She initially presented with fever, generalized weakness, and a rapidly progressing bullous rash affecting her face, neck, upper limbs, and chest. Her medical history included untreated rheumatoid arthritis and chronic bronchitis, for which she had been self-medicating with corticosteroids and other medications. Despite early initiation of high-dose corticosteroids and supportive therapy, her condition deteriorated, leading to septicemia and respiratory failure, necessitating admission to the Infectious Diseases Department. Multidisciplinary management, including immunosuppressive therapy with cyclosporine and targeted antimicrobial treatment, resulted in clinical stabilization and eventual recovery.
Journal Article