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Table 1 Summary of quality assessment and study design for the 18 included papers

From: Risk prediction models for colorectal cancer in people with symptoms: a systematic review

Author, date, country, setting

Qualityf

Outcome

Data collection

Selection of variables

Identification of study population

Identification of outcome cases

Exclusions

Study population

Model development; Case-control studies

Ā Ā Ā Ā Ā Ā Ā 
Ā Ā 

Cases

Controls

Ā Ā 

Cases

Controls

į…ŸHamilton, 2005, UK, primary care [22]

M

CRC

Primary care records from 21 practices

Occurring in at least 2.5Ā % of cases or controls

>40Ā years with primary CRC

5 controls per case matched for sex, general practice and age and alive at point of case diagnosis

Cancer registry at one hospital

Unobtainable records, no consultations in 2Ā years before diagnosis, previous CRC, residence outside Exeter at time of diagnosis.

349

1,744

į…ŸHamilton, 2009, UK, primary care [23]

M

CRC

THIN database

Literature review

> 30Ā years with CRC

Up to 7 controls without CRC matched for practice, sex and age

Diagnosis of CRC within study period

< 2Ā years of full electronic records before date of case diagnosis.

5,477

38,314

Model development and external validation; Case-control study

Ā Ā Ā Ā Ā Ā Ā 
Ā Ā 

Cases

Controls

Ā Ā 

Cases

Controls

į…ŸMarshall, 2011, UK, primary care [24]

H

CRC

BB equation development and CAPER Score external validation

Ā Ā Ā 

See Hamilton, 2009 [23]

As in Hamilton, 2009 plus patients with severe anaemia (Hbā€‰<ā€‰10Ā g/dl), rectal bleeding, abnormal rectal examination or positive FOBT, or without any of abdominal pain, weight loss, diarrhoea or constipation

117

433

Ā Ā 

CRC

CAPER Score development and BB equation external validation

Ā Ā Ā 

See Hamilton, 2005 [22]

Model development and random split-sample internal validation; Cohort studies

Ā Ā Ā Ā Ā Ā 
Ā Ā Ā Ā Ā 

Included

Cases (% of included)

į…ŸHippisley-Cox, 2012, UK, primary care

į…Ÿ(QCancerĀ® (colon)) [25]

H

CRC

QResearch database

'Established predictor variables' and red flag symptoms

30ā€“84 year-old patients registered with practices between 1/1/2000 and 30/09/2010 and without CRC

Incident cancer diagnosis in the 2Ā years after cohort entry recorded in GP records or ONS cause-of-death record

History of CRC, recorded red flag symptomf in the 12Ā months preceding the study date, or missing Townsend deprivation score.

Development

F: 1,172,670

F:4,798 (0.2Ā %)

M:1,178,382

M:4,798 (0.2Ā %)

Internal validation

F: 616,361

F: 2603 (0.2Ā %)

M: 620,240

M:2603 (0.2Ā %)

į…ŸHippisley-Cox, 2013 (female), UK, primary care

į…Ÿ(QCancerĀ® (combined)) [26]

H

CRC and 11 other cancersa

QResearch database

Previous study, and literature review

25ā€“89 year-old patients registered with practices between 1/1/2000 and 1/04/2012 and without CRC

Incident cancer diagnosis in the 2Ā years after cohort entry recorded in GP records or ONS cause-of-death record

Recorded red flag symptomf in the 12Ā months before the study entry date, or missing Townsend deprivation score.

Development

1,240,864

2607 (0.18Ā %)

Internal validation

679,174

1725 (0.25Ā %)

į…ŸHippisley-Cox, 2013 (male), UK, primary care

į…Ÿ(QCancerĀ® (combined)) [27]

H

CRC and 9 other cancersb

QResearch database

Previous study, and literature review

25ā€“89 year-old patients registered with practices between 1/1/2000 and 1/04/2012 and without CRC

Incident cancer diagnosis in the 2Ā years after cohort entry recorded in GP records or ONS cause-of-death record

Recorded red flag symptomf in the 12Ā months before the study entry date, or missing Townsend deprivation score.

Development

1,263,071

3250 (0.26Ā %)

Internal validation

667,603

1356 (0.2Ā %)

Model development; Cross-sectional studies

Ā Ā Ā Ā Ā Ā 
Ā Ā Ā Ā Ā 

Included

Cases (% of included)

į…ŸAdelstein, 2010, Australia, secondary care [32]

H

CRC

Self-administered questionnaire

Not reported

Patientsā€‰>ā€‰18Ā years old scheduled for colonoscopy at hospitals

Complete colonoscopy and histology

Completion of questionnaireā€‰>ā€‰6Ā months before colonoscopy, advanced adenomac, incomplete colon evaluation

7,736

159 (2.1Ā %)

į…ŸAdelstein, 2011, Australia, secondary care [31]

H

CRC

See Adelstein 2010 [32]

Completion of questionnaireā€‰>ā€‰6Ā months before colonoscopy, adenomad, incomplete colon evaluation

6943

159 (2.3Ā %)

į…ŸFijten, 1995, Netherlands, primary care [21]

L

CRC

Patient and doctor questionnaires, and blood sample

Literature review

Patients presenting to 83 GP practices with overt rectal bleeding or a history of visible rectal blood loss in previous 3Ā months.

Medical record review coded using the International Classification of Primary Care for diagnostic classification

Patients aged <18 or >75, pregnancy, urgent admission to hospital or follow-up not available.

290

9 (3.4Ā %)

į…ŸHurst, 2007, UK, secondary care [28]

M

CRC or pre-malignant adenomas

Proforma-based history, examination and blood sample

Not reported

All adult patients referred to a specialist colorectal clinic

Patients tracked until a definitive diagnosis was reached

Patients not further investigated after initial consultation or who did not attend follow up

300

95 (31.7Ā %)

į…ŸLam, 2002, Hong Kong, secondary care [20]

L

CRC or significant neoplasiae

Questionnaire conducted by non-medically trained interviewers

Not reported

New patients attending surgical department for rectal bleeding

Rigid sigmoidoscopy and proctoscopy, followed by barium enema or colonoscopy at the physician's discretion

Refusal for colonoscopy or barium enema

174

29 (16.7Ā %)

į…ŸMahadavan, 2011, UK, secondary care [29]

M

CRC

Self-administered questionnaire, history, faecal, blood and rectal samples

Not reported

All patients >40Ā years referred to a surgical clinic via the 2wwg system for colorectal cancer

Incident diagnosis of CRC within 6Ā months of study entry from primary care or hospital records confirmed histologically

Previous confirmed IBD, GI cancer, investigation of the bowel within the last 6Ā months or absent rectal sampling result

714

72 (10.1Ā %)

Model development and external validation; Cross-sectional study

Ā Ā Ā Ā Ā Ā 
Ā Ā Ā Ā Ā 

Included

Cases (% of included)

į…ŸSelvachandran, 2002, UK, secondary care (WNS) [30] h

H

CRC

Self-administered questionnaire

Not reported

Patients referred by GPs with symptoms suggestive of distal colonic or anorectal disease

Not reported (all patient's received endoscopy)

Not reported

2,268

95 (4.2Ā %)

Model external validation; Cohort study

Ā Ā Ā Ā Ā Ā 
Ā Ā 

Model(s) validated

Ā Ā Ā Ā Ā Ā 

Included

Cases (% of included)

į…ŸCollins, 2012, UK, primary care [33]

H

QCancerĀ® (colon) (female and male) [25]

THIN database

N/A

30ā€“84 year-old patients registered with practices between 1/1/2000 and 30/09/2010 and without CRC

Incident cancer diagnosis of CRC in the 2Ā years after cohort entry

Patients with a history of CRC, a recorded red flag symptomf in the 12Ā months preceding the study date, registered <12Ā months with practice or with invalid dates

Female: 1,075,775

Female:1,676 (0.15Ā %)

Ā Ā Ā Ā Ā Ā Ā Ā Ā 

Male: 1,059,765

Male: 2,036 (0.19Ā %)

Model external validation; Cross-sectional studies

Ā Ā Ā Ā Ā Ā 
Ā Ā 

Model(s) Validated

Ā Ā Ā Ā Ā Ā 

Included (% of eligible)

Cases (% of included)

į…ŸBallal, 2009, UK, secondary care [35]

H

WNS [30]

Self-administered questionnaire

N/A

Patients with colorectal symptoms referred by GPs

A combination of rigid sigmoidoscopy, flexible sigmoidoscopy, colonoscopy or barium enema

Patients thought (on the basis of the referral) most likely to have right-sided CRC, or but did not attend for investigation

3,457

186 (5.4Ā %)

į…ŸHodder, 2005, UK, secondary care [34]

H

WNS [30], Fijten 1995 [21]

Self-administered questionnaire

N/A

Patients referred from primary care with colorectal symptoms

Secondary care investigations - minimum flexible sigmoidoscopy

Not reported

3,302

156 (4.7Ā %)

į…ŸRai, 2008, UK, secondary care [11]

H

WNS [30]

Self-administered questionnaire

N/A

GP referral with any of: lower bowel-related symptoms, unexplained iron deficiency anaemia, positive FOBT, or palpable rectal/abdominal mass

Follow up during course of hospital investigations until a final diagnosis made

Patients admitted hospital as an emergency and subsequently diagnosed with CRC

1,422

83 (5.84Ā %)

Model utility; cohort study

Ā Ā Ā Ā Ā Ā 
Ā Ā 

Model used

Ā Ā Ā Ā 

Outcome measures

Ā 

Included

Interviews

į…ŸHamilton, 2013, UK, primary care [19]

L

Hamilton 2005 [22]

GP usage and outcomes from practices and local trusts; qualitative interviews

Not reported

Risk assessment tools (RATs) supplied to 614 GPs at 164 practices for 6Ā months; interviews with GP cancer network leads and sample of GP users from practices with differing patient demographics.

Number of 2WW referrals and colonoscopies for patients >40; symptoms used in RATs; qualitative interview data.

RATs performed on patients <40; RATs that did not identify the reported symptoms.

1433

23 GP responders

  1. CRC colorectal cancer, ONS office of national statistics, FOBT faecal occult blood test, IBD Inflammatory bowel disease, Hb haemoglobin, WNS Weighted Numerical Score developed by Selvachandran 2002 [30], RAT risk assessment tool
  2. aLung, gastro-oesophageal, pancreatic, renal tract, haematological, breast, ovarian, uterine, cervical and other cancer
  3. bLung, gastro-oesophageal, pancreatic, renal tract, haematological, prostate, testicular, and other cancer
  4. cAdenoma with significant (> 25Ā %) villous features, or high grade dysplasia, including carcinoma-in-situ, or size 10Ā mm or larger
  5. dAdenoma of any size or histology
  6. ePolyp 10Ā mm or larger, or a polyp of any size with a villous histology
  7. frectal bleeding, weight loss, abdominal pain, loss of appetite
  8. g2WW - Two week wait
  9. hThe method of developing the WNS is copyrighted and incompletely reported