Minimal clinically important improvement (MCII) and patient-acceptable symptom state (PASS) in total hip arthroplasty (THA) patients 1 year postoperatively

Figures & data

Figure 1. Patient flow chart.

Table 1. Characteristics of the 1,837 patients who received an invitation to participate in the study in the period from March 1, 2010 to March 1, 2011

Patient characteristics	Patients who agreed to participate	Patients who declined participation	p-value
Population (n (%))	1,335 (73)	502 (27)
Age ^a years, median (range)	68 (23–94)	70 (24–96)	< 0.001
18–50, n	71	27	1.0
50–70, n (%)	706 (53)	223 (44)	0.001
> 70, n (%)	558 (42)	252 (50)	0.001
Female sex, n (%)	720 (54)	295 (59)	0.06
Diagnosis, n (%) ^b
Idiopathic OA	1,175 (90)	397 (84)	0.001
Other arthritis	45	13	0.5
Childhood hip diseases	30	21	0.02
Sequel from fracture	6	5	0.2
Necrosis of femoral head	7	3	0.8

^a Age of patients on date of inclusion start.

^b Idiopathic OA, other arthritis (Mb. Bechterew, other arthritis), childhood hip diseases (congenital hip dislocation, Mb. Calvé-Legg-Perthes, epiphysiolysis, acetabular dysplasia), sequel from fracture (late sequel from fracture of proximal femur), and necrosis of femoral head (atraumatic necrosis of femoral head). Patients with fracture of acetabulum (29 patients accepted, 24 patients declined), traumatic hip dislocation (5 patients accepted, 6 patients declined), and fresh fracture of proximal femur (15 patients accepted, 4 patients declined) were excluded from the study.

Table 2. Minimal clinically important improvement (MCII) for HOOS and EQ-5D. Values are cut-point (95% CI) or AUC ^f

						MCII
		75th percentile approach ^a					Receiver operating characteristic (ROC) approach
PRO	Mean change approach ^a	All patients	Lowest tertile ^b	Middle tertile ^b	Highest tertile ^b		80% speci-ficity ^c	Maximal accuracy ^d	45° tangent line ^e	AUC ^f
Estimated from the hip-specific anchor question: “Overall, how are the problems now in the hip on which you had surgery, compared to before your operation?”
HOOS Pain	24	33	49	31	23		28	33	33	0.91
95% CI	(20–28)	(29–43)	(34–55)	(25–40)	(17–30)		(18–33)	(29–40)	(33–39)	(0.87–0.94)
HOOS-PS	23	35	43	36	25		23	35	34	0.89
95% CI	(19–28)	(25–40)	(32–54)	(25–45)	(20–32)		(15–35)	(27–50)	(31–37)	(0.85–0.94)
HOOS QoL	17	25	31	25	11		19	38	27	0.93
95% CI	(12–22)	(19–30)	(25–45)	(19–28)	(6–19)		(13–31)	(32–39)	(28–39)	(0.91–0.96)
EQ-5D Index ^g	0.14	0.27	0.40	0.10	0.01		0.33	0.16	0.18	0.77
95% CI	(0.10–0.18)	(0.13–0.40)	(0.40–0.48)	(0.07–0.11)	(0–0.05)		(0.13–0.33)	(0.12–0.23)	(0.14–0.24)	(0.70–0.84)
EQ-VAS ^g	7	20	22	20	5		15	23	11	0.76
95% CI	(1–12)	(15–21)	(20–50)	(10–25)	(–13–15)		(10–20)	(3–28)	(12–16)	(0.70–0.82)
Estimated based on the change from preoperatively to postoperatively and the general-health anchor question: “In general, would you say your health is...”
EQ-5D Index ^g	0.31	0.40	0.67	0.34	0.23		0.41	0.18	0.27	0.58
95% CI	(0.29–0.34)	(0.35–0.45)	(0.67–0.68)	(0.34–0.34)	(0.22–0.23)		(0.37–0.44)	(0.07–0.34)	(0.28–0.29)	(0.55–0.62)
EQ-VAS	23	35	51	30	15		35	12	18	0.60
95% CI	(21–25)	(32–40)	(50–55)	(27–30)	(14–15)		(30–40)	(7–14)	(16–20)	(0.57–0.63)

^aAll patients answering “a little better” to the hip–improvement anchor or all patients answering to the general–health anchor 1 category better postoperatively than preoperatively.

^bTertiles (lowest third, middle third, highest third) of preoperative PRO scores.

^cCut–point corresponding to the 80% specificity rule; all patients answering “a little better” and “much better” to the hip–improvement anchor or all patients answering to the general–health anchor 1 category better postoperatively than preoperatively.

^dCut–point corresponding to the smallest residual sum of sensitivity and specificity; all patients answering “a little better” to the hip–improvement anchor or all patients answering to the general–health anchor 1 category better postoperatively than preoperatively.

^eCut–point corresponding to a 45–degree tangent line intersection, equivalent to the point at which the sensitivity and specificity are closest together; all patients answering “a little better” to the hip–improvement anchor or all patients answering to the general–health anchor 1 category better postoperatively than preoperatively.

^f Area under the curve; all patients answering “a little better” and “much better” to the hip–improvement anchor, from the 80% specificity approach, or all patients answering to the general–health anchor 1 category better postoperatively than preoperatively, from the 80% specificity approach.

^g Anchor–PRO correlation < 0.30.

Table 3. Patient–acceptable symptom state (PASS) for HOOS and EQ–5D. Values are cut-point (95% CI) or AUC ^f

	PASS
PRO	Mean score approach ^a	75th percentile approacha				Receiver operating characteristic (ROC) approach
		All patients	Lowest tertile ^b	Middle tertile ^b	Highest tertile ^b	80% specificity ^c	Maximal accuracy ^d	45° tangent line ^e	AUC ^f
Estimated from the hip–specific anchor question: “How would you describe the results of your operation?”
HOOS Pain	91	100	100	100	100	75	75	81	0.90
95% CI	(91–92)	(100–100)	(100–100)	(100–100)	(100–100)	(68–83)	(71–84)	(76–84)	(0.86–0.94)
HOOS-PS	88	100	100	100	100	75	65	75	0.90
95% CI	(87–89)	(100–100)	(95–100)	(100–100)	(100–100)	(65–80)	(61–81)	(71–76)	0.87–0.94)
HOOS QoL	83	100	100	100	100	50	58	56	0.94
95% CI	(82–85)	(100–100)	(94–100)	(100–100)	(100–100)	(44–56)	(51–59)	(51–64)	(0.92–0.97)
EQ-5D-Index	0.90	1	1	1	1	0.72	0.77	0.77	0.92
95% CI	(0.89–0.91)	(1–1)	(1–1)	(1–1)	(1–1)	(0.72–0.77)	(0.73–0.80)	(0.73–0.79)	(0.90–0.94)
EQ-VAS	82	95	90	90	95	70	70	70	0.86
95% CI	(81–83)	(90–95)	(90–90)	(90–95)	(95–98)	(70–80)	(71–76)	(71–71)	(0.82–0.89)
Estimated based on the postoperative answers to the general–health anchor question: “In general, would you say your health is...”
EQ-5D Index	0.92	1	1	1	1	0.82	0.79	0.82	0.84
95% CI	(0.91–0.92)	(1–1)	(1–1)	(1–1)	(1–1)	(0.78–0.84)	(0.79–0.83)	(0.79–0.83)	(0.81–0.88)
EQ-VAS	85	95	90	94	95	75	72	75	0.89
95% CI	(84–86)	(94–95)	(90–95)	(90–95)	(95–98)	(70–80)	(71–76)	(73–80)	(0.86–0.91)

^aAll patients with an “excellent”, “very good” or “good” postoperative operation result or general health.

^bTertiles (lowest third, middle third, highest third) of preoperative PRO scores.

^cCut–point corresponding to the 80% specificity rule; all patients with an “excellent”, “very good”, or “good” operation result or general health postoperatively.

^DCut–point corresponding to the smallest residual sum of sensitivity and specificity; all patients with an “excellent”, “very good”, or “good” operation result or general health postoperatively.

^ECut–point corresponding to a 45–degree tangent line intersection, equivalent to the point at which the sensitivity and specificity are closest together; all patients with an “excellent”, “very good”, or “good” operation result or general health postoperatively.

^FArea under the curve; all patients with an “excellent”, “very good”, or “good” operation result or general health postoperatively.

Table 4. Patient–acceptable symptom state (PASS) for different subgroups; mean (95% CI)

					Subgroups
PRO	Males	Females	p-value ^a	Idiopatic OA	Other diagnoses	p-value ^a	< 50 years	50–70 years	< 70 years p-valueb
Estimated by the mean score method using the anchor question: “How would you describe the results of your operation?”
HOOS Pain	93	90	<0.001	92	90	0.3	93	92	90	0.03
95% CI	(92–94)	(89–91)		(91–92)	(87–93)		(91–95)	(91–93)	(89–92)
HOOS-PS	90	86	<0.001	88	86	0.3	91	89	85	<0.001
95% CI	(88–91)	(85–88)		(87–89)	(83–90)		(89–94)	(88–90)	(84–87)
HOOS QoL	85	82	0.005	84	77	0.008	80	83	84	0.4
95% CI	(84–87)	(80–83)		(83–85)	(72–82)		(75–85)	(82–85)	(82–86)
EQ-5D Index	0.91	0.89	0.002	0.90	0.85	0.004	0.90	0.91	0.89	0.03
95% CI	(0.90–0.92)	(0.88–0.90)		(0.90–0.91)	(0.82–0.89)		(0.87–0.93)	(0.90–0.92)	(0.87–0.90)
EQ-VAS	85	80	<0.001	82	80	0.3	86	84	79	<0.001
95% CI	(83–86)	(78–81)		(81–83)	(77–84)		(82–89)	(83–85)	(77–81)
Estimated by the mean score method using the anchor question: “In general, would you say your health is...”
EQ-5D Index	0.93	0.91	0.04	0.92	0.87	0.003	0.91	0.92	0.92	0.9
95% CI	(0.92–0.94)	(0.90–0.92)		(0.91–0.93)	(0.84–0.90)		(0.88–0.94)	(0.91–0.93)	(0.90–0.93)
EQ-VAS	87	83	<0.001	85	83	0.2	88	86	83	0.01
95% CI	(86–88)	(82–85)		(84–86)	(80–86)		(85–90)	(85–87)	(82–85)

^a Welch’s t–test.

^b W–test.