© 2006 Case Designs Reports that cover the management of a single patient or a series of patients

© 2006

Case Designs

Reports that cover the management of a single

patient or a series of patients

Evidence-based Chiropractic © 2006

Three types of case designs

1. 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


Three types of case designs (cont.)

2. Case Series– More than 2 case reports in a single paper

3. 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


The purposes and limitations of case reports

Purposes Detect rare conditions Educational value Learn how other doctors manage certain cases Generate hypotheses

Limitations Susceptible to many biases Unable to test hypotheses Does not determine the effectiveness of an

intervention Unable to generalize results to other patients

or practices


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


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


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


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


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


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


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


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


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


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


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


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


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


ABA design (cont.)

Days or weeksDays or weeks


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


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


SSTSDs graph

Level -Changes in the value of the dependent variable before and after the intervention

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)

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

The slope of a trend refers to the rate of change of the data or the angle that is formed by the data


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


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


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


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


ABAC design (cont.)

The change in level from B to C could the result of a carry-over effect

The change in level from B to C could the result of a carry-over effect


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


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


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


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


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


Intervention appliedIntervention applied

Intervention appliedIntervention applied

Intervention applied Intervention applied

Multiple baseline design


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


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


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


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


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


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


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


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



• 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



• 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


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


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



• 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



• 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


Graphing SSTSDs

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

Oswestry Low Back Pain Disability Questionnaire or Neck Pain Disability Index

Oswestry Low Back Pain Disability Questionnaire or Neck Pain Disability Index Numeric pain scale with 0 = no pain and 10 = worst pain imaginable

Numeric pain scale with 0 = no pain and 10 = worst pain imaginable

O

X

Observationphase

Treatmentphase


Hypothetical graph

O

X

O

X

O

X

O

X

O

X

O

X

O

X

O

X

O

X

O

X

O

X

O

X

Neck Pain Disability Index

0-10 NumericPain Scale


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


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



• Does the Abstract provide an accurate description of the case and its implications? – Readers often assume that abstracts are

accurate, but they may not be – Frequently the only part of an article that is

actually read– Abstract should be used as a screening tool

to locate interesting articles, then read them



• Is the case really unique or uncommon?– It is sometimes appropriate to replicate the

same topic in several case reports, but eventually new studies should involve more sophisticated designs

– However, it is common to find many case reports on the same topic about harm associated with treatment

• Necessary to observe patterns of adverse events that are related to a particular form of treatment



• Was the literature review adequate? – May be brief, but should call attention to the

most current relevant research on the topic – An explanation of how the literature relates to

the current case– References should be derived from valid

sources; principally peer-reviewed journals



• Was a rationale for reporting the case presented that effectively highlights its importance?– An explanation of why the report was written – Is the information already common

knowledge?– Should include a compelling argument to

justify the need for writing of the case report• If weak, consider not reading the rest of the article



• Was the case adequately described in the Case Description section?– Described clearly and concisely, yet

comprehensively– Including the patient’s health history,

examination, diagnosis, treatment, and final outcome

• Details of the treatment (e.g., type, location, and frequency)

• Should not include irrelevant findings



• Was the study population described adequately? – A case should be explicitly defined– Selection criteria

• Based on diagnosis; examination, laboratory, or radiographic findings; or condition severity

– For example, in a series of neck pain patients• Case would be defined as pain of mechanical

origin, no disc herniation, no radicular pain, etc.



• Were the outcome measures suitable for the given clinical circumstances? – Must be quantifiable (e.g., pain scores or

ROM)• A vague statement such as “there was less lumbar

muscle spasm” is inadequate

– Novel diagnostic tests should be fully described, together with normal values



• Did the author present convincing evidence in support of the diagnosis that was presented? – The diagnosis should be supported by

evidence derived from the results of the case and the literature review

– Differential diagnoses that were considered and why they were eliminated



• Did the author point out the study’s limitations and suggest alternate explanations? – Limitations should be clearly identified– Other possible explanations for the results of

the case should be mentioned • e.g., natural progression of the condition,

extraneous factors, and placebo effects • No control group and limited generalizability



• Were suggestions for future research offered? – This is one of the chief reasons for writing

case reports– Authors should suggest how the topic should

be investigated in future studies

• Were suggestions provided to assist other practitioners in the management of similar cases?



• Was enough evidence presented to support the author’s conclusions? – Conclusions should flow logically from the

case description – No unsupported statements should be offered

• Especially about the effectiveness of the intervention

• Or suggest that other practitioners will obtain similar results

Documents

© 2006 Case Designs Reports that cover the management of a single patient or a series of patients