Table 3 Subgroup analyses for rectal bleeding, change in bowel habit and anaemia

Symptom item and subgroup	No of studies	Sensitivity (95% CI)	Specificity (95% CI)	Positive LR (95% CI)	p Value for the difference	Negative LR (95% CI)	p Value for the difference
Rectal bleeding
Study setting
Primary care-based	2	37% (26% to 49%)	73% (46% to 93%)	1.49 (0.80 to 2.77)		0.84 (0.72 to 0.98)
Secondary care-based	11	70% (61% to 77%)	51% (43% to 59%)	1.35 (1.21 to 1.50)	0.76	0.69 (0.59 to 0.81)	0.08
Lower GI investigation used
Colonoscopy	8	69% (58% to 80%)	51% (37% to 65%)	1.42 (1.16 to 1.74)		0.69 (0.51 to 0.93)
Other investigations	6	58% (43% to 78%)	55% (37% to 71%)	1.23 (1.11 to 1.36)	0.21	0.79 (0.68 to 0.91)	0.43
Symptom data collection
Via questionnaire	6	59% (42% to 75%)	56% (35% to 75%)	1.31 (1.16 to 1.49)		0.75 (0.64 to 0.87)
Not reported	5	65% (53% to 76%)	54% (40% to 67%)	1.33 (1.10 to 1.62)		0.76 (0.61 to 0.93)
Via clinical history	3	76% (49% to 94%)	43% (23% to 64%)	1.34 (0.82 to 2.17)	0.99	0.56 (0.18 to 1.78)	0.88
Number of centres
Single-centre studies	9	66% (52% to 78%)	54% (38% to 69%)	1.40 (1.19 to 1.64)		0.73 (0.58 to 0.92)
Multicentre studies	5	62% (50% to 74%)	50% (36% to 63%)	1.24 (1.10 to 1.39)	0.23	0.76 (0.66 to 0.87)	0.77
Study sample size
<500 patients	8	63% (49% to 77%)	53% (40% to 66%)	1.35 (1.07 to 1.72)		0.78 (0.57 to 1.05)
⩾500 patients	6	65% (52% to 77%)	51% (34% to 68%)	1.27 (1.15 to 1.41)	0.64	0.76 (0.66 to 0.82)	0.88
Change in bowel habit
Study setting
Primary care-based	2	32% (11% to 59%)	67% (41% to 89%)	0.99 (0.76 to 1.29)		1.01 (0.88 to 1.16)
Secondary care-based	9	43% (23% to 64%)	69% (56% to 80%)	1.38 (1.10 to 1.73)	0.06	0.77 (0.59 to 1.01)	0.08
Lower GI investigation used
Colonoscopy	5	22% (9% to 38%)	83% (75% to 89%)	1.26 (0.62 to 2.57)		1.00 (0.86 to 1.16)
Other investigations	6	57% (39% to 74%)	56% (45% to 66%)	1.26 (1.00 to 1.58)	0.99	0.73 (0.50 to 1.05)	0.12
Symptom data collection
Via questionnaire	5	46% (20% to 73%)	64% (44% to 81%)	1.23 (1.07 to 1.41)		0.85 (0.71 to 1.02)
Not reported	5	32% (4% to 69%)	71% (57% to 84%)	1.05 (0.63 to 1.75)	0.56	0.87 (0.57 to 1.34)	0.92
Number of centres
Single-centre studies	7	51% (32% to 70%)	62% (50% to 73%)	1.34 (1.02 to 1.76)		0.75 (0.50 to 1.12)
Multicentre studies	4	26% (5% to 56%)	79% (59% to 94%)	1.18 (0.82 to 1.70)	0.58	0.93 (0.80 to 1.08)	0.33
Study sample size
<500 patients	6	26% (14% to 41%)	79% (67% to 88%)	1.30 (0.77 to 2.20)		0.99 (0.85 to 1.14)
⩾500 patients	5	57% (33% to 80%)	56% (42% to 69%)	1.26 (0.98 to 1.60)	0.92	0.69 (0.44 to 1.07)	0.13
Anaemia
Lower GI investigation used
Colonoscopy	5	10% (5% to 17%)	91% (87% to 94%)	1.24 (0.74 to 2.08)		1.00 (0.96 to 1.06)
Other investigations	2	37% (0% to 91%)	87% (79% to 94%)	2.21 (0.68 to 7.19)	0.38	0.63 (0.25 to 1.58)	0.33
Symptom data collection
Via questionnaire	4	25% (6% to 50%)	90% (87% to 92%)	1.91 (0.94 to 3.91)		0.88 (0.75 to 1.03)
Not reported	2	4% (0% to 15%)	91% (77% to 98%)	0.48 (0.13 to 1.79)	0.07	1.06 (0.96 to 1.17)	0.05
Number of centres
Single-centre studies	3	5% (1% to 13%)	91% (82% to 97%)	0.59 (0.21 to 1.67)		1.05 (0.96 to 1.15)
Multicentre studies	4	25% (6% to 50%)	90% (87% to 92%)	1.91 (0.94 to 3.91)	0.07	0.88 (0.75 to 1.03)	0.08
Study sample size
<500 patients	5	17% (1% to 47%)	90% (84% to 94%)	1.57 (0.67 to 3.72)		0.91 (0.75 to 1.10)
⩾500 patients	2	12% (8% to 17%)	90% (89% to 91%)	1.18 (0.78 to 1.79)	0.56	0.98 (0.93 to 1.04)	0.47

LR, likelihood ratio.