Case Designs

1. Case Designs Reports that cover the management of a single patient or a series of patients

2. Three types of case designs • Case Report • An article that describes the clinical course of 1 or 2 patients • Typically consist of complaints, examination findings, diagnosis, treatment, and outcome • Case reports often provide early evidence of new diseases, treatments, or adverse effects • No hypothesis, data analysis, or generalizable conclusion is possible Evidence-based Chiropractic

3. Three types of case designs (cont.) • Case Series • Two or more case reports in a single paper • Single-subject time series design • A type of case report that tracks a patient’s condition using multiple sequential assessments during a treatment phase and a phase when they are not being treated Evidence-based Chiropractic

4. Case Reports • From JMPT Instructions for Authors • “. . . accounts of the diagnosis and treatment of unusual, difficult, or otherwise interesting cases that may have independent educational value or may contribute to better standardization of care for a particular health problem when correlated with similar reports of others.” Evidence-based Chiropractic

5. Case Reports (cont.) • They report new or unusual aspects of practice that are of interest to and are highly relevant to practitioners • They are the fundamental building blocks of scientific inquiry in health care • Many times case reports are the first line of evidence in clinical inquiry • Often lead to progressively more complex studies Evidence-based Chiropractic

6. Case Reports (cont.) • May be thought of as clinician-to-scientist communications because they provide ideas for future research • Considered a descriptive design because they do not report on any experimental data • They are not merely anecdotal, however, because they provide important data to other practitioners about patient management Evidence-based Chiropractic

7. Case Reports (cont.) • They are usually retrospective • However, they can be prospective when patient care is planned out ahead of time • Certain elements must be present in a case report in order to be publishable • e.g., the basic structure of a scholarly article with Abstract, Introduction, Case Description, and Discussion sections Evidence-based Chiropractic

8. Practitioners like them • They are easier to read and shorter than other types of journal articles • Quick to prepare, so new information is rapidly available to practitioners • Highly relevant to clinical practice • Depict the full management of a patient • While experimental studies typically involve only a specific intervention Evidence-based Chiropractic

9. Four types of case reports • The unique case, which has not (or very rarely) been described in the literature • The case with an unexpected association between two or more conditions • Usually involves a patient who presents with more than one rare condition • The relationship may or may not be causal, but cannot determine from a case study Evidence-based Chiropractic

10. Four types of case reports (cont.) • The case of an unusual presentation • For example, a patient falls on their buttocks and injures their lower back; a cervical fracture is also found, but no neck pain • The case of unexpected development in a condition • Typically implies either a therapeutic or an adverse effect to an intervention Evidence-based Chiropractic

11. Limitations of case reports • Natural progression of the condition • The issue can never be fully addressed without comparing treatment and control groups in a RCT • The outcome might have been the same without the treatment • Improvement may have been the result of a placebo effect Evidence-based Chiropractic

12. Limitations of case reports (cont.) • The patient may have had an atypical response to the treatment • Other patients who receive the same treatment for the same condition may respond differently • Care is delivered in an uncontrolled environment • Extraneous factors may affect the outcome Evidence-based Chiropractic

13. The purposes and limitations of case reports Evidence-based Chiropractic

14. The structure of a case report • The structure deviates slightly from other research articles • Abstract, Introduction, Case Description, Discussion, and References • The Case Description section replaces Methods and Results • It is the most important section of a case report Case Description Evidence-based Chiropractic

15. Abstract • Provides a brief summary of the article • Usually about 250 words • Its content should convey the most important features of the case and why it is worth reporting • May be in narrative or structured format • Most journals now require structured Evidence-based Chiropractic

16. Abstract (cont.) • Structured abstracts are composed of a series of labeled paragraphs • e.g, Purpose, Methods, Results, and Conclusions • JMPT requires them for all original reports, literature reviews, clinical guidelines, and case reports Evidence-based Chiropractic

17. Introduction • Typically quite brief and provides: • Background information about the condition • What motivated the case report • i.e., what is unique, unexpected, or unusual about the case • A short review of the literature that will be expanded in the Discussion section • Information about the condition, such as etiology and standard treatments Evidence-based Chiropractic

18. Case Description • Presents the case with regard to the diagnosis, intervention, and outcome • Equivalent to the combined Methods and Results sections of other types of articles • Should include relevant information in chronological order • No material that does not directly deal with the problem (e.g., negative tests) Evidence-based Chiropractic

19. Case Description (cont.) • The case description should include: • Chief complaint • Complete medical history • Diagnostic tests • Diagnosis • Treatment (if provided) • Outcome • Follow-up actions (if any) Evidence-based Chiropractic

20. Case Description (cont.) • Treatment may not be involved • The patient may have been referred to another provider • For instance, a chiropractic patient with a headache that was actually caused by a cerebral aneurism • Case description would explain patient management leading to the diagnosis Evidence-based Chiropractic

21. Discussion • a.k.a., Comments section • Why the case is considered important and educational • Explains unanswered questions • Offers an interpretation of the study’s findings • Must be supported by evidence Evidence-based Chiropractic

22. Discussion (cont.) • Alternative explanations may be suggested and why they were rejected • Limitations to either the methods that were employed or the evidence that was presented should be mentioned • The need for further research and the types of studies that should be conducted Evidence-based Chiropractic

23. Preparation of case reports • Does not typically require approval from an Institutional Review Board • However, patient confidentiality should be respected • Personal information that might identify the patient should not be used • Patient photographs require written consent prior to submitting the report for publication Evidence-based Chiropractic

24. Reasons case reports are returned to authors for revision • Claims of cause-and-effect relationships between interventions and outcomes • Lack of information about the reliability and validity of measurements • Lack of detail about the examination and the intervention • Lack of detail about decision making Evidence-based Chiropractic

25. The evidence-based case report • Designed to illustrate the process of locating and applying evidence to clinical circumstances • How evidence can be applied during the various phases of patient care • Informative even when little or no high-quality evidence is available • They do not report new findings Evidence-based Chiropractic

26. Case series • A report of the management of more than a few patients who have something in common • The same diagnosis, history, treatment, etc. • For example, 10 patients with carpal tunnel syndrome • Patients receive an intervention and then their outcomes are assessed report on adverse events Evidence-based Chiropractic

27. Case series (cont.) • A case series may also report on adverse events • The patients’ data are aggregated and explored to see if there are any common factors of etiology • They are typically based on the retrospective analysis of patient records from a single practice or institution Evidence-based Chiropractic

28. Case series (cont.) • They provide valuable information about case management, trends in outcomes, and clues about causation • However, there is no comparison group, which severely limits its value as evidence • Results of case series may be compared to historical controls, but this is not a legitimate comparison Evidence-based Chiropractic

29. Case series are highly susceptible to bias • Selection bias • There are no criteria for patient selection, so the author may selectively choose patients • Consecutive case selection helps • Observation bias • The doctor’s beliefs or expectations may affect outcomes • There is no blinding to prevent this bias Evidence-based Chiropractic

30. Case series are highly susceptible to bias (cont.) • Natural progression of the condition • May make the results look much better than what they really are • Less of a problem than in single case reports because a group of cases is involved • Regression to the mean • Patients with initial extreme scores will likely have more normal scores on re-evaluation Evidence-based Chiropractic

31. Case series shouldaddress the following • Clearly defined study question • Well-described study population • Well-described intervention • Valid outcome measures • Appropriate statistical analyses • Well-described results Evidence-based Chiropractic

32. Case series shouldaddress the following • Conclusions supported by the data • Acknowledgement of funding sources Evidence-based Chiropractic

33. Meta-analyses of case reports or case series • Occasionally seen in the literature • Sometimes they can draw important new conclusions from the literature • Limited statistical analyses may be done • e.g., totals, means, proportions, correlation • Conclusions may be proven wrong after more definitive research has been done Evidence-based Chiropractic

34. Single-subject time series designs (SSTSDs) • A study that involves a single patient • Repeated measures are taken while an intervention is applied and withdrawn • The objective is to observe differences in the outcome measures during each phase • Improvement during the intervention phase may mean that the treatment is effective for that patient Evidence-based Chiropractic

35. SSTSDs (cont.) • The patient acts as their own control during the no treatment phase • Other names for SSTSD • Single case experimental design • Time series design • Small-n design • n-of-1 trial • Within-subject comparison Evidence-based Chiropractic

36. Baseline phase • Typically the initial phase of a SSTSD • At least 3 repeated measures of the outcomes are taken prior to starting treatment to show that the condition is stable • Reveals the natural state of the patient’s condition and becomes the standard for evaluating the effect of treatment Evidence-based Chiropractic

37. Intervention phase • The phase in which treatment is started • Usually follows the baseline phase • Outcomes are measured at least 3 times • Duration should be the same as the baseline phase • Changes in the outcome during this phase can be attributed to the treatment Evidence-based Chiropractic

38. Enhanced validity of SSTSDs • Evidence derived from SSTDs is more convincing than case reports • Repeated measures during the treatment and non-treatment phases reduces the likelihood that the results are due to chance • Outcome measures should be objective, measurable, and clinically relevant Evidence-based Chiropractic

39. Enhanced validity of SSTSDs (cont.) • Can be the strongest evidence available regarding an individual patient • The best way to establish whether a specific treatment is effective for an individual patient • Results may improve confidence in therapeutic decisions • However, results cannot be generalized because they only involve a single subject Evidence-based Chiropractic

40. SSTSDs are quasi-experimental • Independent variables are manipulated (applied and then withdrawn) as in experimental research • Case studies may include manipulation of the independent variable but do not measure changes of the dependent variable over repeated observations Evidence-based Chiropractic

41. AB design • Where - A = baseline or observation phase B = intervention phase • A fairly weak design because it has very little control over threats to internal validity • The outcome must change dramatically to support a cause-and-effect relationship Evidence-based Chiropractic

42. ABA design • Involves 3 phases: • Baseline, intervention, and follow-up • The minimum number a SSTSD should incorporate • Provides much stronger evidence in support of a cause-and-effect relationship • Especially if the follow-up phase returns to near baseline levels Evidence-based Chiropractic

43. ABA design (cont.) Days or weeks Evidence-based Chiropractic

44. ABA design (cont.) • Additional phases can be added (ABAB) if there is little distinction between phases • Sometimes called the withdrawal design • Helps to rule out confounding variables so that the treatment effect can be seen more clearly • Spontaneous remission, placebo effects, cyclical conditions may still influence results Evidence-based Chiropractic

45. ABA design (cont.) • Chronic conditions that are fairly stable are best suited for SSTSDs • Condition should be reversible and return to pre-treatment values in A phase • Acute or unstable conditions are not suitable • Outcome measures would vary a great deal between phases with or without the intervention Evidence-based Chiropractic

46. SSTSDs graph Level - Changes in the value of the dependent variable before and after the intervention Trend - Changes in the direction of the dependent variable (accelerating, decelerating, stable or variable) The slope of a trend refers to the rate of change of the data or the angle that is formed by the data Evidence-based Chiropractic

47. Analyzing SSTSD graphs • Can be visually inspected to assess patient response by level, trend, and slope • The data can also be statistically analyzed • Somewhat controversial • Both methods were reported to be equally useful • Although graphs are more popular and are easier to understand Evidence-based Chiropractic

48. Statistical analysis of SSTSD data • Binomial test • The probability of getting y number of successes (a positive treatment effect) by chance, given x number of events (pairs of baseline and treatment phases) • Limited value because it takes at least five AB pairs, all with a positive treatment effect, to reach the 0.05 level of significance Evidence-based Chiropractic

49. Statistical analysis of SSTSD data (cont.) • Paired t-test or repeated measures ANOVA • Their non-parametric equivalents may be used instead • Provide more power than the binomial test because they consider both the direction and magnitude of the treatment effect in each pair Evidence-based Chiropractic

50. ABAC design • C represents an alternate treatment • Consists of • An initial observation phase • Followed by treatment B phase • Then a second observation phase • Finally alternate treatment C phase • Must consider the possibility of carry-over effects from the first phase of treatment Evidence-based Chiropractic