Table 3.

Power gains associated with dichotomous versus specific radiographic endophenotype descriptors

Study parameters							Estimated parameters
SNP	Definition of cases	Definition of controls	N cases	N controls	EAF	OR	Power (%)	N cases	N controls	N total
rs754106	Hip OA with superior JSN	Hip OA with non-superior JSN	1265	552	0.54	0.72	18.45	2416	1054	3470
	Hip OA with superior JSN	Population-based	1265	6500	0.54	0.91	0.05	10 669	54 821	65 490
	Hip OA	Population-based	1817	6500	0.54	1.01	0.00	>1 000 000	>3 577 325	>4 577 325
rs73023563	Hip OA with superior JSN	Hip OA with non-superior JSN	1265	552	0.19	1.63	57.78	1571	686	2257
	Hip OA with superior JSN	Population-based	1265	6500	0.20	1.07	0.00	31 513	161 925	193 438
	Hip OA	Population-based	1817	6500	0.19	0.94	0.00	43 995	157 384	201 379
rs17050727	Hip OA with axial/medial JSN	Hip OA with non-axial/medial JSN	425	1392	0.14	1.65	28.62	705	2309	3014
	Hip OA with axial/medial JSN	Population-based	425	6500	0.14	1.43	4.89	1168	17 864	19 032
	Hip OA	Population-based	1817	6500	0.14	1.00	0.00	∞	∞	∞
rs6766414	Hip OA with hypertrophic response	Hip OA with non-hypertrophic response	531	1286	0.24	1.42	12.40	1139	2758	3897
	Hip OA with hypertrophic response	Population-based	531	6500	0.24	1.25	0.92	2199	26 918	29 117
	Hip OA	Population-based	1817	6500	0.24	1.00	0.00	∞	∞	∞
rs61837881	Hip OA with hypertrophic response	Hip OA with non-hypertrophic response	531	1286	0.24	1.39	7.69	1298	3144	4442
	Hip OA with hypertrophic response	Population-based	531	6500	0.24	1.33	7.15	1323	16 195	17 518
	Hip OA	Population-based	1817	6500	0.24	1.06	0.00	40 187	143 762	183 949
rs16869403	Hip OA with atrophic response	Hip OA with non-atrophic response	267	1550	0.10	2.11	58.36	330	1916	2246
	Hip OA with atrophic response	Population-based	267	6500	0.10	1.93	42.25	383	9324	9707
	Hip OA	Population-based	1817	6500	0.10	1.05	0.00	115 540	413 324	528 864

For each variant and stratum we present power (%) based on study-specific effect size, effect allele frequency and case/control ratio from the GWAS on Illumina610k. Similarly we estimated the sample size required to have 80% power to detect the associated signals with genome-wide significance (p=5×10⁻⁸).

EAF, effect allele frequency; GWAS, genome-wide association studies; JSN, joint space narrowing; OA, osteoarthritis; SNP, single nucleotide polymorphism.