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Case Designs

Case Designs

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Case Designs

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  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 • More than 2 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. The purposes and limitations of case reports Evidence-based Chiropractic

  5. 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

  6. 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

  7. 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

  8. 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

  9. 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

  10. 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

  11. 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

  12. 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

  13. 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

  14. 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

  15. 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

  16. 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

  17. 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

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

  19. 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

  20. 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

  21. 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

  22. 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

  23. 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

  24. 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

  25. 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

  26. ABAC design (cont.) The change in level from B to C could the result of a carry-over effect Evidence-based Chiropractic

  27. Features of conditions that are suitable for the SSTSD • Condition is chronic • Condition is stable • Spontaneous remission is not likely • Previous treatment has had limited success • No concurrent treatment is involved Evidence-based Chiropractic

  28. Cyclical conditions • Difficult to investigate with SSTSDs • However, replication of cycles by using additional phases in which the outcomes consistently improve when the treatment is applied can add support to a cause-and-effect relationship Evidence-based Chiropractic

  29. Types of treatment used with SSTSDs • Treatments that have a rapid onset of action when applied and a rapid termination of action when withdrawn are best • Treatments that continue to act even after they are stopped are less desirable because they require a washout period to allow the outcome measures to return to a baseline state Evidence-based Chiropractic

  30. Multiple baseline design (a.k.a., replicated AB design) • Involves 3 or more subjects who have similar complaints and are provided a similar treatment • The basic AB design is carried out on each patient, but • Baselines are of differing lengths of time • There is no withdrawal of treatment • Can help control for extraneous variables Evidence-based Chiropractic

  31. Multiple baseline design (cont.) • As usual, differences in the measurements are analyzed between phases within each subject • There is also a comparison across subjects • Cause-and-effect is strengthened • Because it is not likely that extraneous factors occurred by chance at the specific time treatment was started on each patient Evidence-based Chiropractic

  32. Multiple baseline design Intervention applied Intervention applied Intervention applied Evidence-based Chiropractic

  33. Simultaneous replication design • Similar to the multiple baseline design, but all patients start the study at the same time and their scores are tracked concurrently • Patient care is not necessarily provided concurrently In multiple baseline studies Evidence-based Chiropractic

  34. Simultaneous replication design (cont.) • Treatment is started on the first patient, then in sequence with the other study participants • The first patient is started on the treatment at the outset of the study • Treatment is withheld from subsequent patients until a treatment effect is discernible in the preceding patient Evidence-based Chiropractic

  35. Simultaneous replication design (cont.) • This design helps control for confounding factors • When treatment is given to one patient and the dependent variable changes, while the baseline measures of the untreated patients remain unchanged, the chance that something outside the study caused the change is reduced Evidence-based Chiropractic

  36. The n-of-1 RCT • Described by Sackett et al • A single patient is randomly assigned to receive a placebo versus an authentic treatment or medication • Blinding is possible when medication is involved since the doctor and patient do not know whether the real medication or a placebo is being used Evidence-based Chiropractic

  37. The n-of-1 RCT (cont.) • Difficult to perform with manipulation as the independent variable • The chiropractor would always know if the treatment was a placebo • The patient would most likely be aware of their assignment • Although n-of-1 studies with limited randomization and blinding are feasible for chiropractic patients Evidence-based Chiropractic

  38. SSTSD studies are feasible for practicing chiropractors • To determine the best form of treatment for a particular patient • SSTSDs are are the best form of evidence for this task • To reassure the patient and practitioner that the treatment is actually helping • To contribute articles to peer reviewed journals Evidence-based Chiropractic

  39. When to do SSTSD studies • When there are doubts about the effectiveness of a planned treatment in a specific patient • The patient may have already tried other practitioners and therapies without benefit • SSTSD may be useful to see if the planned treatment actually results in improvement Evidence-based Chiropractic

  40. When to do SSTSDs (cont.) • It is not clear if a treatment is actually helping • To the patient or practitioner • The patient is undergoing another type of treatment or self-treating • And it is thought that this treatment may be ineffective or interfering with the patient’s progress Evidence-based Chiropractic

  41. When to do SSTSDs (cont.) • The doctor or patient thinks some of the patient’s symptoms may be caused by the treatment • There is doubt about what the optimal combination of therapies or frequency of care should be Evidence-based Chiropractic

  42. When to do SSTSDs (cont.) • Any time the patient or practitioner has questions about the effectiveness of a patient’s treatment • The patient is agreeable and even enthusiastic about participating • Is actually a partnership between the clinician and the patient • May not work if the patient is non-compliant Evidence-based Chiropractic

  43. SSTSD ethical concerns • Denying treatment to patients during the observation phase • Only applies to cases where withholding treatment would actually be harmful • Chiropractic candidates for SSTSDs are patients with chronic conditions that are not likely to deteriorate during periods of time without treatment Evidence-based Chiropractic

  44. SSTSD ethical concerns (cont.) • The patient can still receive other forms of treatment in a SSTSD • Only the specific intervention under investigation must be withheld • Patients should be fully informed about what is involved in the study • Signed informed consent • They have the right to withdraw at any time and for any reason Evidence-based Chiropractic

  45. SSTSD ethical concerns (cont.) • If the intent of patient care includes the performance of a research project, the patient should be informed they are the object of a scientific investigation • Qualifies as research when • Data is collected with the intent to publish the results in a journal or present at a conference • There is intent to produce new information beyond current standard care Evidence-based Chiropractic

  46. SSTSD ethical concerns (cont.) • Must obtain approval from a legitimate Institutional Review Board before beginning clinical research, even in a private practice setting • It may actually be unethical to continue to provide an intervention on an ongoing basis without testing its effectiveness at some point Evidence-based Chiropractic

  47. GraphingSSTSDs Form can be used to track patients with low back or neck pain The patient does not need to return to the office during observation phase, but can take home questionnaires and complete them at scheduled times Observation phase O Treatment phase X Oswestry Low Back Pain Disability Questionnaire or Neck Pain Disability Index Numeric pain scale with 0 = no pain and 10 = worst pain imaginable Evidence-based Chiropractic

  48. Hypothetical graph O O O O O O X X Neck Pain Disability Index X X X X O O O O 0-10 Numeric Pain Scale O O X X X X X X Evidence-based Chiropractic

  49. Appraising case reports • Not much information is available on how to appraise case reports and case series • Yet appraisal is necessary in order to gain as much as possible from reading and to avoid wasting time with poorly written articles Evidence-based Chiropractic

  50. Appraising case reports (cont.) • They should adhere to the general format of a scholarly publication and contain the required sections • Abstract, Introduction, Case Description, Discussion, and References • A red flag if any of these elements are missing or labeled incorrectly • Allow for atypical manuscript requirements and use of synonyms Evidence-based Chiropractic