Ethnicity and impact on the receipt of cognitive–behavioural therapy in people with psychosis or bipolar disorder: an English cohort study

Objectives (1) To explore the role of ethnicity in receiving cognitive–behavioural therapy (CBT) for people with psychosis or bipolar disorder while adjusting for differences in risk profiles and symptom severity. (2) To assess whether context of treatment (inpatient vs community) impacts on the relationship between ethnicity and access to CBT. Design Cohort study of case register data from one catchment area (January 2007–July 2017). Setting A large secondary care provider serving an ethnically diverse population in London. Participants Data extracted for 30 497 records of people who had diagnoses of bipolar disorder (International Classification of Diseases (ICD) code F30-1) or psychosis (F20–F29 excluding F21). Exclusion criteria were: <15 years old, missing data and not self-defining as belonging to one of the larger ethnic groups. The sample (n=20 010) comprised the following ethnic groups: white British: n=10 393; Black Caribbean: n=5481; Black African: n=2817; Irish: n=570; and ‘South Asian’ people (consisting of Indian, Pakistani and Bangladeshi people): n=749. Outcome assessments ORs for receipt of CBT (single session or full course) as determined via multivariable logistic regression analyses. Results In models adjusted for risk and severity variables, in comparison with White British people; Black African people were less likely to receive a single session of CBT (OR 0.73, 95% CI 0.66 to 0.82, p<0.001); Black Caribbean people were less likely to receive a minimum of 16-sessions of CBT (OR 0.83, 95% CI 0.71 to 0.98, p=0.03); Black African and Black Caribbean people were significantly less likely to receive CBT while inpatients (respectively, OR 0.76, 95% CI 0.65 to 0.89, p=0.001; OR 0.83, 95% CI 0.73 to 0.94, p=0.003). Conclusions This study highlights disparity in receipt of CBT from a large provider of secondary care in London for Black African and Caribbean people and that the context of therapy (inpatient vs community settings) has a relationship with disparity in access to treatment.


Conclusions: This study highlights disparity in receipt of CBT for Black African and
Caribbean people. This study also highlights that context of therapy (inpatient versus community settings) impacts on disparity in access to treatment.

Strengths and Limitations
 A key strength of this study is that the data were from a near-complete case register of a large secondary care mental health service provider; which has a near monopoly on mental health provision in its catchment area.
 Published data are available on the tools used for extracting information about CBT which indicates high degrees of precision (95%) and sensitivity (96%).
 A limitation of this study is that it was not possible to assess access to other types of psychological intervention (e.g. Family Therapy).  This study was not able to assess the offer of therapy (only receipt), consequently it is unclear if there are ethnic differences in whether or not therapy is offered to Black service users.

Research Questions and rationale:
There is a lack of information about the extent of inequalities experienced by ethnic minority groups with serious mental illness, despite well-recognised adverse outcomes in certain minority groups. Furthermore, there is a paucity of information about the role that risk and symptom severity plays in treatment disparity (including access to psychological therapy) for ethnic minority groups. Consequently, using all the case records from a large secondary care mental healthcare provider, this study set out to answer the following questions:

Demographic, Clinical and Treatment data extracted and operationalised
Demographic data retrieved included gender, marital status, ethnicity and age. All of the demographic data was retrieved at the point of data extraction (31 st   We retrieved data about the CBT session regarding: whether the service user was an inpatient or outpatient at the time of contact; whether the contact was face-to-face or remote (e.g. via telephone); and whether the contact was in a one to one, or group session. In line with National Standard guidelines definition of access (NHS England, 2016), the current investigation assessed whether participants had at least one documented session of CBT.
NICE guidelines for psychosis recommend that CBT is delivered "over at least 16 planned session (sic)" (NICE, 2014a, p.589). NICE guidelines for bipolar disorder recommend that a depressive episode should be treated with between 16 to 20 sessions of CBT (NICE, 2014b).
Consequently, a 16-session criterion was also adopted as a more stringent definition of a course of CBT. Jolley et al., (2015) operationalised CBT therapy completion as at least 5 sessions. Supplementary analyses were conducted utilising this less stringent definition of a course of CBT treatment. Analyses of the 5 and 16 session criteria were restricted to participants who had at least one documented session of CBT (n=5197). Participants were also excluded from analyses regarding the 5 and 16 session criteria if they were currently receiving CBT at data extraction and had not received a minimum of 5 or 16 sessions of CBT, which resulted in n=100 and n=220 participants being excluded respectively (see Figure 1). CBT that was currently on-going was defined as anyone who had a CBT session in the 6 weeks prior to data extraction.

Ethical Considerations
The anonymised dataset has been approved by the NHS REC for secondary analysis (Oxford C Research Ethics Committee, reference18/SC/0372). This particular project received ethical approval from the Lancaster University Faculty of Health and Medicine Research Ethics Committee and approval from the CRIS Oversight Committee.

Patient and Public Involvement
This specific project was reviewed, commented on and approved by the CRIS Oversight Committee, which is chaired by a service user representative. Furthermore, the development of the CRIS system was informed by consultation with service users (Fernandes et al., 2013).

Analysis
Logistic regression models were built using multivariable procedures in Stata 12.
Models were adjusted for demographic data (gender, age, IMD, and marital status), diagnoses (psychosis/bipolar disorder), and risk/severity variables (as described previously).
Analysesare presented as: crude associations; adjustments for demographic data and diagnosis (Step 1); and adjustments for demographic data, diagnosis and the risk/severity variables (Step 2).

Descriptive Statistics
The final sample consisted of 20,010 cases, Figure 1 displays the flow of cases through the study.    Ethnicity and impact on the implementation of CBT suicidal ideation, feelings of hopelessness, high levels of distress, no feelings of control, and referral to the crisis team. However, a history of a substance misuse disorder diagnosis and plans to end life were associated with a decreased likelihood of reported receipt of CBT. reported high levels of distress and lifetime referral to crisis team). However, several factors associated with increased odds of ever receiving a documented session of CBT (Table 2) were not significantly associated with having a minimum of 16 documented sessions (i.e. lifetime inpatient admittance, history of non-adherence, lethal means used in suicide attempt, reported suicidal ideation, reported feelings of hopelessness, reported feelings of a lack of control).

Ethnicity and reported receipt of CBT as an inpatient
Analyses were restricted to participants who had been an inpatient (N= 9417) and associations investigated with receipt or not of CBT in this setting. Unadjusted and adjusted associations are displayed in Table 4 Table 4).

Recording of clinical risk
The crude estimates indicated that several variables indicative of higher clinical risk and severity were associated with increased odds of having a (single) documented session of CBT (Table 2). We considered that this may be because CBT is better recorded (rather than more likely to be delivered) for those at an increased risk (e.g. of harming themselves, suicide, harming others) and proposed that, if defensive practice resulted in better note keeping, this would be most likely evident in the structured fields. Consequently, as a supplementary sensitivity analysis, using the entire sample (N=20,010), models assessing reported receipt of CBT were re-run omitting entries identified in the structured fields, (i.e. just using data derived from free text). However, this analysis continued to indicate an association between Black African group membership and significantly lower odds of Adjusted and unadjusted odds ratios are presented in Supplementary Table 5.

Influence of time
Additional analyses were conducted to assess if changes over time affected referral practices for psychological treatments. To this end, a variable was created indicating participants who had received a diagnosis of psychosis or bipolar affective disorder after the mid-point of the data collection window (i.e. after the 16 th of April 2012). Models considering ethnicity and reported receipt of CBT were re-run including the variable indicating the date at which diagnosis was given. This analysis also indicated that the Black African group were significantly less likely to receive CBT than the White British group (OR 0.72, CI 0.65 to 0.81, p<.001), suggesting that this finding was not influenced by the date diagnosis was given (see Supplementary Table 6). In the fully adjusted model, receiving a diagnosis of psychosis or bipolar affective disorder after the midpoint of the data collection window was associated with decreased odds of a documented session of CBT (OR 0.77, CI 0.71 to 0.83, p<.001). Further, analysis was conducted to assess if there was an interaction between time and ethnicity; however, a likelihood ratio test indicated that fitting this interaction term did not significantly improve the model: Chi 2 (4) =5.25, p= .26.

Discussion
This investigation found that after adjustment for numerous indicators of risk and severity, in comparison to White British counterparts, Black African people with bipolar disorder or psychosis were less likely to have a documented session of CBT, a finding which was robust to a number of sensitivity analyses. After adjustment for indicators of risk and symptom severity in comparison to White British people, Black Caribbean people were also less likely to receive CBT as inpatients, and were less likely to receive the minimum 16 Ethnicity and impact on the implementation of CBT sessions recommended by national guidelines. This study also found that regardless of ethnicity people who had their first documented session of CBT as an inpatient were less likely to receive a minimum of 16 sessions of CBT (and a similar effect was also noted in supplementary analyses of a minimum 5 documented sessions and documented receipt of CBT as an outpatient). In addition, regardless of ethnicity indicators of higher risk and severity of symptoms were typically associated with higher odds of receiving CBT; however, these associations between risk status and receipt of CBT were less consistent in analyses of a minimum 16 documented sessions.
To our knowledge, this study has used the largest sample to date to assess ethnic differences in access to CBT for people with psychosis or bipolar affective disorder. This study utilised a case register from a large mental healthcare provider serving a socially and ethnically diverse geographic catchment. Furthermore, the data were sourced from the full electronic health record, using a case register with near-complete coverage of people receiving mental healthcare for these diagnoses. The study utilised a tool to extract information about CBT from structured fields and free text, an approach which has been shown to have high positive predictive value and sensitivity values in previous work (Colling et al., 2017). Consequently, this study likely provides a highly accurate picture of access to CBT delivered by mental health services within the catchment. Of note, despite having recognised high incidence rates of psychosis (Jongsma et al., 2017)  First access of CBT as an inpatient was associated with lower odds of receiving further CBT sessions. There are numerous potential explanations. For example, coercive practice in inpatient settings has been well documented and this may potentially impact on subsequent engagement (Department of Health and Social Care, 2018). Alternatively, our finding may be related to differences in recovery styles (Drayton, Birchwood & Trower, 1998). An avoidant recovery style (referred to as sealing over) has been linked to poorer engagement with services (Tait, Birchwood & Petertrower, 2004), and it is possible that some people are receptive to psychological therapy at the point of crisis (i.e. during inpatient stay), but once there is a diminution of symptoms they 'seal over' which reduces engagement.
Step 1 Adjusted for Ethnicity + Gender + Age + IMD decile + Marital Status + diagnosis: psychosis/bipolar Step 2 Adjusted for Ethnicity + Gender + Age + IMD decile + Marital Status + diagnosis: psychosis/bipolar + Substance use diagnosis + inpatient admittance + treated under the MHA + Structured risk assessment items (entered separately) + Referred to crisis team + Treated at A & E + Referred to assertive outreach + forensic history  Reference groups are a non-affirmative response to the item. The n for the reference group is the number of people included in the analysis (N=4977) -the number of people with an affirmative response.
Step 1 Adjusted for Ethnicity + Gender + Age + IMD decile + Marital Status + diagnosis: psychosis/bipolar Step 2 Adjusted for Ethnicity + Gender + Age + IMD decile + Marital Status + diagnosis: psychosis/bipolar + Substance use diagnosis + inpatient admittance + treated under the MHA + Structured risk assessment items (entered separately) + Referred to crisis team + Treated at A & E + Referred to assertive outreach + forensic history + First CBT as inpatient

Supplementary Data 3
Supplementary Data 3 contains crude estimates and adjusted multivariable logistic regression models regarding ethnicity and having a minimum of 5 sessions of CBT.

Supplementary Data 4
Supplementary Data 4 contains crude estimates and adjusted multivariable logistic regression models regarding ethnicity and reported receipt of CBT as an outpatient.

Supplementary Data 5
Supplementary Data 5 contains crude estimates and adjusted multivariable logistic regression models regarding ethnicity and reported receipt of CBT in the unstructured clinical notes (i.e. just using data derived from free text not structured fields). .

Strengths and Limitations
 A key strength of this study is that the data were from a near-complete case register of a large secondary care mental health service provider; which has a near monopoly on mental health provision in its catchment area.
 Published data are available on the tools used for extracting information about CBT which indicates high degrees of precision (95%) and sensitivity (96%).
 A limitation of this study is that it was not possible to assess access to other types of psychological intervention (e.g. Family Therapy).  This study was not able to assess the offer of therapy (only receipt), consequently it is unclear if there are ethnic differences in whether or not therapy is offered to Black service users.   [4] and are less likely to receive medication associated with fewer side effects. [5] In the Netherlands, ethnic minority groups are more likely to be compulsorily detained for treatment and less likely to be recommended for outpatient treatment. [6] A prospective study in the UK, found significant ethnic differences in Mental Health Act 2007 (MHA) assessments and detentions, with Black Africans having higher rates than any other ethnic group. [7] However, when controlling for diagnosis, age, risk and social support there were no significant ethnic differences in detention. [7] Similarly, Singh [8] found no significant differences between ethnic groups in MHA detention whilst controlling for variables such as risk and social support. These studies raise the possibility that treatment differences could be accounted for by ethnic differences in factors such as: self-harm and suicide attempt, [9] psychosis symptom profiles, [10] deprivation, [11] and substance use. [12] UK national guidelines recommend Cognitive Behavioural Therapy for the treatment and prevention of psychosis (CBTp), as CBTp has demonstrated robust evidence of its

Research Questions and rationale:
There is a lack of information about the extent of inequalities experienced by ethnic minority groups with serious mental illness, despite well-recognised adverse outcomes in certain minority groups. Furthermore, there is a paucity of information about the role that risk and symptom severity plays in treatment disparity (including access to psychological therapy) for ethnic minority groups. Consequently, using all the case records from a large secondary care mental healthcare provider, this study set out to answer the following questions:

Method Study Design and Setting
The data, which were generated as part of routine care, were derived from clinical  No upper limit was set on age. Cases were excluded if: they were under the age of 15 (a criterion which has been previously applied to this cohort; [39]); they had a diagnosis of an organic/non-functional disorder; or there were missing data regarding marital status, including individuals recorded as Indian, Pakistani, or Bangladeshi was also included in the sample. This investigation utilised the same approach of defining and grouping ethnicity which has been applied to CRIS data previously. [39,41]  Automated natural language processing (NLP) algorithms (see [42]) are used to determine the presence and prescribed 'value' of variables contained in free text.  We retrieved data about the CBT session regarding: whether the service user was an inpatient or outpatient at the time of contact; whether the contact was face-to-face or remote (e.g. via telephone); and whether the contact was in a one to one, or group session. In line  Analyses of the 5 and 16 session criteria were restricted to participants who had at least one documented session of CBT (n=5197). Participants were also excluded from analyses regarding the 5 and 16 session criteria if they were currently receiving CBT at data extraction and had not received a minimum of 5 or 16 sessions of CBT, which resulted in n=100 and n=220 participants being excluded respectively (see Figure 1). CBT that was currently ongoing was defined as anyone who had a CBT session in the 6 weeks prior to data extraction.

Ethical Considerations
The anonymised dataset has been approved by the NHS REC for secondary analysis (Oxford C Research Ethics Committee, reference18/SC/0372). This particular project received ethical approval from the Lancaster University Faculty of Health and Medicine Research Ethics Committee and approval from the CRIS Oversight Committee.

Patient and Public Involvement
This specific project was reviewed, commented on and approved by the CRIS Oversight Committee, which is chaired by a service user representative. Furthermore, the development of the CRIS system was informed by consultation with service users. [38]  Models were adjusted for demographic data (gender, age, IMD, and marital status), diagnoses (psychosis/bipolar disorder), and risk/severity variables (as described previously).
Analysesare presented as: crude associations; adjustments for demographic data and diagnosis (Step 1); and adjustments for demographic data, diagnosis and the risk/severity variables (Step 2).

Descriptive Statistics
A total of 5351 cases were excluded due to missing data relating to marital status (n=3678), Index of Multiple Deprivation (n=1308), ethnicity (n=362), gender (n=2) and age (n=1).The final sample consisted of 20,010 cases, Figure 1 displays the flow of cases through the study.

(FIGURE 1)
The majority of cases were White British (n = 10393, 51.9%), the next largest ethnic group were Black Caribbean people who made up 27.4% of the sample (n=5481). There were more male cases (n=10457, 52.3%) than female and the majority were single (n=17097, 85.4%).      (Table 2) were not significantly associated with having a minimum of 16 documented sessions (i.e. lifetime inpatient admittance, history of non-adherence, lethal means used in suicide attempt, reported suicidal ideation, reported feelings of hopelessness, reported feelings of a lack of control).

Ethnicity and reported receipt of CBT as an inpatient
Analyses were restricted to participants who had been an inpatient (N= 9417) and associations investigated with receipt or not of CBT in this setting. Unadjusted and adjusted associations are displayed in Table 4 Table 4).

Recording of clinical risk
The crude estimates indicated that several variables indicative of higher clinical risk and severity were associated with increased odds of having a (single) documented session of CBT (Table 2). We considered that this may be because CBT is better recorded (rather than more likely to be delivered) for those at an increased risk (e.g. of harming themselves, suicide, harming others) and proposed that, if defensive practice resulted in better note keeping, this would be most likely evident in the structured fields. Consequently, as a supplementary sensitivity analysis, using the entire sample (N=20,010), models assessing reported receipt of CBT were re-run omitting entries identified in the structured fields, (i.e. just using data derived from free text). However, this analysis continued to indicate an association between Black African group membership and significantly lower odds of receiving CBT than White British group membership (OR 0.76, CI 0.63 to 0.92, p=.004).
Adjusted and unadjusted odds ratios are presented in Supplementary Table 5.

Influence of time
Additional analyses were conducted to assess if changes over time affected referral practices for psychological treatments. To this end, a variable was created indicating participants who had received a diagnosis of psychosis or bipolar affective disorder after the mid-point of the data collection window (i.e. after the 16 th of April 2012). Models considering ethnicity and reported receipt of CBT were re-run including the variable indicating the date at which diagnosis was given. This analysis also indicated that the Black  1  2  3  4  5  6  7  8  9  10  11  12  13  14  15  16  17  18  19  20  21  22  23  24  25  26  27  28  29  30  31  32  33  34  35  36  37  38  39  40  41  42  43  44  45  46  47  48  49  50  51  52  53  54  55  56  57  58  59  African group were significantly less likely to receive CBT than the White British group (OR 0.72, CI 0.65 to 0.81, p<.001), suggesting that this finding was not influenced by the date diagnosis was given (see Supplementary Table 6). In the fully adjusted model, receiving a diagnosis of psychosis or bipolar affective disorder after the midpoint of the data collection window was associated with decreased odds of a documented session of CBT (OR 0.77, CI 0.71 to 0.83, p<.001). Further, analysis was conducted to assess if there was an interaction between time and ethnicity; however, a likelihood ratio test indicated that fitting this interaction term did not significantly improve the model: Chi 2 (4) =5.25, p= .26.

Statement of principal findings
This investigation found that after adjustment for numerous indicators of risk and severity, in comparison to White British counterparts, Black African people with bipolar disorder or psychosis were less likely to have a documented session of CBT, a finding which was robust to a number of sensitivity analyses. After adjustment for indicators of risk and symptom severity in comparison to White British people, Black Caribbean people were also less likely to receive CBT as inpatients, and were less likely to receive the minimum 16 sessions recommended by national guidelines. This study also found that regardless of ethnicity people who had their first documented session of CBT as an inpatient were less likely to receive a minimum of 16 sessions of CBT (and a similar effect was also noted in supplementary analyses of a minimum 5 documented sessions and documented receipt of CBT as an outpatient). In addition, regardless of ethnicity indicators of higher risk and severity of symptoms were typically associated with higher odds of receiving CBT; however, these associations between risk status and receipt of CBT were less consistent in analyses of a minimum 16 documented sessions.  1  2  3  4  5  6  7  8  9  10  11  12  13  14  15  16  17  18  19  20  21  22  23  24  25  26  27  28  29  30  31  32  33  34  35  36  37  38  39  40  41  42  43  44  45  46  47  48  49  50  51  52  53  54  55  56  57  58  59

Strengths and limitations of the study
To our knowledge, this study has used the largest sample to date to assess ethnic differences in access to CBT for people with psychosis or bipolar affective disorder. This study utilised a case register from a large mental healthcare provider serving a socially and ethnically diverse geographic catchment. Furthermore, the data were sourced from the full electronic health record, using a case register with near-complete coverage of people receiving mental healthcare for these diagnoses. The study utilised a tool to extract information about CBT from structured fields and free text, an approach which has been shown to have high positive predictive value and sensitivity values in previous work. [19] Consequently, this study likely provides a highly accurate picture of access to CBT delivered by mental health services within the catchment. Of note, despite having recognised high incidence rates of psychosis, [37] the catchment is not dissimilar to other parts of London and UK urban areas on several sociodemographic metrics; [35,36] the results of this investigation may generalise to other urban and semi-urban multicultural areas in England, a notion which is supported by ethnic disparity in access to therapy indicated in nationally representative data. [2] By accessing a large data set of complete clinical records we were able to contribute novel findings relating to the impact of risk and pathways on engagement with CBT.
However, one limitation of this investigation is that it was not possible to extract information from the BRC Case Register about other psychological therapies, some of which are recommended by national guidelines and delivered routinely within the services analysed (e.g. Family Intervention; [13]). It is possible therefore that disparity in access to CBT may be accounted for by ethnic differences in preference for therapy type, although this has not been suggested to be the case in other studies of national data from the UK. [2] Another limitation is that although this study likely displays an accurate picture of service users who received CBT it was not possible to derive information about the offer of CBT. If service users are not  1  2  3  4  5  6  7  8  9  10  11  12  13  14  15  16  17  18  19  20  21  22  23  24  25  26  27  28  29  30  31  32  33  34  35  36  37  38  39  40  41  42  43  44  45  46  47  48  49  50  51  52  53  54  55  56  57  58  59  An additional limitation of this study is we did not extract information regarding the length of inpatient stay. The consequence of this is we do not know the impact of length of stay on the likelihood that someone receives CBT. It is feasible that people who have very short inpatient stays are less likely to receive CBT than those who spend longer in that environment.

Strengths of this study in relation to other research
Our findings replicate those observed for unselected community residents from a nationally representative sample, namely less equitable access to CBT for ethnic minority groups. [2] Previous investigations which have explored ethnic disparities in access/engagement with CBT in samples with psychosis have not differentiated between Black African and Black Caribbean people, [2,19,23, 24] despite the two groups typically having different migratory histories and different factors influencing pathways into treatment for psychosis.
[49] The current investigation was able to define more specific ethnic categories providing a more nuanced understanding of ethnicity and access to CBT.

Comparisons with previous research
Previous research has highlighted that more positive symptoms in psychosis increase referrals for CBT.

Implications of this research and suggestions for future research
Our study suggests that, within clinical settings, further work is needed to ensure there is parity in access to CBT. In practice, this might include ensuring that CBT is systematically offered to groups who are less likely to receive treatment. It is also feasible that further work is needed to ensure that CBT is more acceptable to Black groups which might be achieved by culturally-adapting interventions.

Supplementary Data 3
Supplementary Data 3 contains crude estimates and adjusted multivariable logistic regression models regarding ethnicity and having a minimum of 5 sessions of CBT.

Supplementary Data 4
Supplementary Data 4 contains crude estimates and adjusted multivariable logistic regression models regarding ethnicity and reported receipt of CBT as an outpatient.

Supplementary Data 5
Supplementary Data 5 contains crude estimates and adjusted multivariable logistic regression models regarding ethnicity and reported receipt of CBT in the unstructured clinical notes (i.e. just using data derived from free text not structured fields).
Step 1 Adjusted for Ethnicity + Gender + Age + IMD decile + Marital Status + diagnosis: psychosis/bipolar Step 2 Adjusted for Ethnicity + Gender + Age + IMD decile + Marital Status + diagnosis: psychosis/bipolar + Substance use diagnosis + inpatient admittance + treated under the MHA + Structured risk assessment items (entered separately) + Referred to crisis team + Treated at A & E + Referred to assertive outreach + forensic history  1  2  3  4  5  6  7  8  9  10  11  12  13  14  15  16  17  18  19  20  21  22  23  24  25  26  27  28  29  30  31  32  33  34  35  36  37  38  39  40  41  42  43  44  45  46  47  48  49  50  51  52  53  54  55  56  57  58  59 Table 6 Crude and adjusted associations from logistic regression models for at least one recorded session of CBT (inpatient or outpatient) adjusting for time Variable N Odds Ratio (95% Confidence Interval) Crude Associations# Step 1 Step Present key elements of study design early in the paper pp.7-8 Setting 5 Describe the setting, locations, and relevant dates, including periods of recruitment, exposure, follow-up, and data collection p.7 & p.9 Participants 6 (a) Give the eligibility criteria, and the sources and methods of selection of participants. Describe methods of follow-up pp.8-9 (b) For matched studies, give matching criteria and number of exposed and unexposed n/a Variables 7 Clearly define all outcomes, exposures, predictors, potential confounders, and effect modifiers. Give diagnostic criteria, if applicable pp.10-11 Data sources/ measurement 8 For each variable of interest, give sources of data and details of methods of assessment (measurement). Describe comparability of assessment methods if there is more than one group pp.10-11