Comparison of breast cancer surrogate subtyping using a closed-system RT-qPCR breast cancer assay and immunohistochemistry on 100 core needle biopsies with matching surgical specimens

Table 2 Concordance between STRAT4 and IHC for core biopsy and surgical specimens

Comparisons	Target	True pos	True neg	False pos	False neg	OPA (%)	PPA (%)	NPA (%)	PPV (%)	NPV (%)	Kappa (95% CI^a)
STRAT4 vs IHC, both CNB	ER	85	12	1	2	97.0	97.7	92.3	98.8	85.7	0.87 (0.73–1.0)
	PR	76	13	9	2	89.0	97.4	59.1	89.4	86.7	0.64 (0.44–0.83)
	Ki-67	37	39	22	2	76.0	94.9	63.9	62.7	95.1	0.54 (0.39–0.69)
	HER2	18	69	13	0	87.0	100.0	84.1	58.1	100.0	0.66 (0.49–0.82)
STRAT4 vs IHC, both surgical specimen	ER	85	11	2	2	96.0	97.7	84.6	97.7	84.6	0.82 (0.65–0.99)
	PR	78	14	5	3	92.0	96.3	73.7	94.0	82.4	0.73 (0.55–0.91)
	Ki-67	39	39	14	8	78.0	83.0	73.6	73.6	83.0	0.56 (0.40–0.72)
	HER2	17	74	8	1	91.0	94.4	90.2	68.0	98.7	0.73 (0.57–0.89)
CNB vs surgical specimen, both STRAT4	ER	86	13	0	1	99.0	99	100	100	93	0.96 (0.87–1.0)
	PR	81	13	4	2	94.0	98	76	95	87	0.78 (0.61–0.95)
	Ki-67	44	32	15	9	76.0	83	68	75	78	0.51 (0.35–0.68)
	HER2	21	65	10	4	86.0	84	87	68	94	0.65 (0.49–0.82)

^aCohen’s kappa κ-values: > 0.8 indicated very good agreement, between 0.6 and 0.8 indicated good agreement between 0.4 and 0.6 was considered as moderate agreement, < 0.4 as fair, < 0.2 as poor agreement

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