Table 1. Summary of the included studies.

Author, Year	Number of patients Mean age (range) Sex (♂:♀)	Patient population Setting	Prior colorectal cancer	Reference standard and number or percentage of patients receiving it Follow-up	Prevalence of symptoms/signs/patient characteristics		PLR
Du Toit et al, 2006	265 pt ND years (45–ND years)♂ND: ♀ND	Pt ⩾ 45 years with new onset rectal bleeding, irrespective of other symptoms. Rural practice in England; four doctors; one registrar.	5.7% (15 of 265)	Rigid sigmoidoscopy with barium enaema (most patients), flexible sigmoidoscopy, or colonoscopy. (p 69) Follow-up: unclear	Patient characteristics Age 45–54 years Age 55–64 years Age 65–74 years Age ⩾75 years	% Population 19% 28% 24% 29%	PLR 0.7 0.2 1.8 1.4
Ellis and Thompson 2005	319 pt 59 years (35–94 years) ♂143: ♀176	Pt 35 years consulting their GP with rectal bleeding 19 GPs in 3 practices in the United Kingdom: 1 market town/rural community; 1 suburban; 1 inner-city	3.4% (11 of 319)	-Flexible sigmoidoscopy (219 pt) -Patient questionnaire (47 pt) -Flexible sigmoidoscopy & questionnaire (53 pt) -Barium enaema (37 pt) -Colonoscopy (24 pt) Follow-up:18 months	Symptoms/signs/patient characteristics Bleeding and CIBH (n=119) Bleeding and CIBH (loose +/− frequent) (n=83)	% Population 37% 26%	PLR 2.4 1.3
					Bleeding and no perianal symptoms (n=63)	20%	2.9
					Bleeding CIBH and abdominal pain (n=67)	21%	1.0
					Dark blood (n=31)	10%	2.1
					Age ⩾ 60 years (n=155)	49%	1.5
					Blood on paper only (n=82)	26%	0.6
					Large volume of blood (n=79)	25%	0.3
					First time rectal bleeding (n=106)	33%	1.2
					Blood mixed with stool (n=33)	10%	0.7
Fijten et al, 1995	269 pt 42 years (18–75 years) ♂118: ♀151	Patients ⩾ 18 years and ⩽75 years with overt rectal bleeding as a reason for consult or history of recent (<3 month) blood loss visible. 83 GPs in the South of the Netherlands	3.3% (9 of 269)	A total of 31% had further investigations initiated by the GP by means of sigmoidoscopy (9%) colon roentenography (9%), proctoscopy (8%), sonography (6%) and colonoscopy (2%). Some patients underwent more than one investigation. Follow-up: at least 1 year (mean 20 months) Medical records and information of the GP.	Symptoms/signs Blood seen:  Mixed with stool only  On stool or mixed with stool only Others or  combinations	% Population 5% 20% 45%	PLR 8.0 3.8 0.4
					Abdominal pain	50%	0.7
					Change in bowel habit (more frequently or diarrhoea or variously, but not constipation)	29%	2.9
					Pain at night	19%	0.0
					Decreased appetite	16%	0.7
					Nausea	25%	0.4
					Weight loss	16%	3.0
					Family history of abdominal disease	31%	0.0
					Previous history of rectal bleeding	36%	0.0
					Pale conjunctivae	2%	5.8
					Perianal eczema	6%	6.2
					Rectal palpation (n=208):
					Haemorrhoid	7%	2.5
					Tumour	0%	1.0
					Abnormal prostate	1%	22.3
					Patient characteristics	% Population	PLR
					Age 18–29 years	23%	0.0
					Age 30–39 years	26%	0.0
					Age 40–49 years	20%	0.0
					Age 50–59 years	15%	0.7
					Age 60–75 years	15%	7.2
					Male	44%	1.8
					Laboratory test results	% Population	PLR
					Anaemia (Hb♀ < 7.5 mmol l−1 ♂<8.5 mmol l−1)	5%	6.6
					ESR high (♀>28 mm h−1♂>8.5 mm h−1)	9%	4.2
					ESR high (>30 mm h−1)	4%	8.8
					High white blood cell count (>109 per litre) (n=219)	9%	5.8
					Haemoccult ⩾1 positive out of 3	15%	2.3
Heintze et al, 2005	422 pt ND years (ND–ND years) ♂199: ♀222	Patients >15 years 94 GPs in Germany	4.0% (17 of 422)	Diagnostic work-up: Sonography (52 pt) Rectoscopy (29 pt) Sigmoidscopy (26 pt) Colonoscopy (195 pt) Treatment by GP (93pt) Follow-up: Unclear	Symptoms/signs/patient characteristics Male Age <50 years Age ⩾50 years Age 15–24 years	% Population 53% 38% 62% 2%	PLR 1.3 0.2 1.5 0.0
					Age 25–34 years	11%	0.4
					Age 35–44 years	14%	0.3
					Age 45–54 years	16%	0.5
					Age 55–64 years	28%	1.3
					Age 65–74 years	18%	1.7
					Age 75–84 years	8%	0.5
					Age 85–94 years	2%	8.4
					Weight loss	3%	1.3
					Changed bowel habit	18%	1.2
					Abdominal pain	24%	0.7
					Anaemia	6%	2.4
					Dark red blood	12%	1.1
					Blood mixed with stool	19%	1.9
					Family history of colon carcinoma	7%	3.6
Mant et al, 1989	145 pt 58 years (40–95 years) ♂77: ♀68	Pt ⩾ 40 years who consulted the GP for rectal bleeding 48 GPs in Australia	11% (16 of 145)	-Total colonoscopy (104 pt) -Endoscopy to at least 30 cm and an air-contrast barium enaema (32 pt)-Investigations not complete, but an obvious source was found, e.g. rectal cancer at proctoscopy. (9 pt) Follow-up: unclear	Symptoms/signs/patient characteristics Male First-degree relative with CRC (n=143) Abdominal pain (n=144)	% Population 53% 14% 30%	PLR 0.8 0.9 0.8
					Change in bowel habit (n=143)	39%	1.0
					Feeling of incomplete evacuation of rectum	29%	1.1
					Weight Loss (n=143)	10%	1.3
					Anal itch	25%	0.2
					Pain on defecation	21%	0.6
					Anal protrusion noticed by patient	21%	0.3
					Dark red blood (n=144)	16%	1.7
					Blood mixed with faeces (n=140)	36%	2.2
					Haemorrhoids identified by GP	51%	0.5
Metcalf et al, 1996	99 pt 58 years (40–86 years) ♂42: ♀57	Patients ⩾ 40 years 17 GPs in Newcastle upon Tyne, England	8.1% (8 of 99)	Questionnaire (99pt) Colonoscopy (98pt) Barium enaema in any patients whom a satisfactory colonoscopy was not completed. (1pt) Follow-up: Unclear (Practices participated between 1–9 months)	Symptoms/signs/patient characteristics Dark red blood loss Blood mixed with stool Diarrhoea Associated slime	% Population 31% 46% 32% 28%	PLR 1.2 1.4 0.9 1.4
					Constipation	39%	0.3
					Change in bowel habit	39%	1.3
					Abdominal pain	42%	0.9
					Weight loss	15%	1.8
Norrelund and Norrelund 1996(1)	208 pt 42 years (18–75 years) ♂97: ♀111	Patients ⩾ 40 years presenting with a first episode of rectal bleeding 96 GPs from Denmark	15.4% (32 of 208)	GPs were asked to arrange either a barium enaema or a colonoscopy at the first consultation. Follow-up: 32 months Colorectal cancer microscopically verified or yearly letter to GP	Symptoms/signs/patient characteristics Male Age 40–69 years Age 70–79 years Age 80+ years	% Population 47% 68% 25% 7%	PLR 1.3 0.3 3.3 2.2
					Weight loss	11%	1.6
					Abdominal pain	23%	1.5
					Change in bowel habits	29%	2.6
					Discomfort	27%	1.3
Norrelund and Norrelund 1996(2)	156 pt 42 years (18–75 years) ♂71: ♀85	Patients ⩾ 40 years first bleeding episode or change in usual bleeding pattern 112 GPs from Denmark	14.1% (22 of 156)	GPs were asked to arrange either a barium enaema or a colonoscopy at the first consultation. Follow-up: 22 months CRC microscopically verified or yearly letter to GP	Symptoms/signs/patient characteristics Male Age 40–69 years Age 70–79 years Age 80+ years	% Population 46% 72% 21% 7%	PLR 1.0 0.7 2.4 0.6
					Weight loss	14%	1.8
					Abdominal pain	27%	2.2
					Change in bowel habits	31%	1.6
					Discomfort	26%	0.9
					New rectal bleeding	69%	0.8
Wauters et al, 2000	386 pt ND years (ND-ND years) ♂ND: ♀ND	Network of sentinel practices in Belgium	7.0% (27 of 386)	Investigations such as endoscopy were not systematically performed. ‘To obtain the number of all new cases of cancer, we sent recall letters to the practices every six months and at the end of the follow-up period.’ (p 998) Follow-up (clinical): 18–30 months	Symptoms/signs/patient characteristics Age <50 years Age 50–59 years Age 60–69 years Age 70–79 years Age ⩾ 80 years Pain	% Population 37% 15% 18% 17% 13% 9%	PLR 0.1 0.2 1.7 3.6 0.8 0.0
					Spasms	29%	0.8
					Weight loss	6%	2.5
					Palpable tumour	5%	6.1

Abbreviations: CIBH=change in bowel habit; ND=no data available. The page numbers refer to the original text of the included studies.