Table 2.

Validity of diagnoses codes of bone metastases and skeletal-related events (SREs) subsequent to breast cancer in the Danish National Registry of Patients (NRP): January 1st, 2000–December 31st, 2000

		Medical chart review
	NRP	Yes	No
Any bone metastases or SRE	Yes	11	4
	No	8	77
	Total	19	81
	Sensitivity		11/19 = 0.58 (0.34–0.80)
	Specificity:		77/81 = 0.95 (0.88–0.99)
	PPV		11/(11 + 4) = 0.73 (0.45–0.92)
	NPV		77/(77 + 8) = 0.91 (0.82–0.96)
Bone metastases only	Yes	6	1
	No	13	80
	Total	19	81
	Sensitivity		6/19 = 0.32 (0.13–0.57)
	Specificity:		80/81 = 0.99 (0.93–1.00)
	PPV		6/(6 + 1) = 0.86 (0.42–1.00)
	NPV		80/(80 + 13) = 0.86 (0.77–0.92)
Any SRE	Yes	9	3
	No	3	85
	Total	12	88
	Sensitivity		9/12 = 0.75 (0.43–0.95)
	Specificity:		67/71 = 0.97 (0.90–0.99)
	PPV		9/(9 + 3) = 0.75 (0.43–0.95)
	NPV		85/(85 + 3) = 0.97 (0.90–0.99)
Radiation therapy	Yes	6	4
	No	4	86
	Total	10	90
	Sensitivity		6/10 = 0.60 (0.26–0.88)
	Specificity:		86/90 = 0.96 (0.89–0.99)
	PPV		6/(6 + 4) = 0.60 (0.26–0.88)
	NPV		85/(86 + 4) = 0.94 (0.88–0.98)
Pathological fracture	Yes	1	1
	No	2	96
	Total	3	97
	Sensitivity		1/3 = 0.33 (0.04–0.91)
	Specificity:		96/97 = 0.99 (0.94–1.00)
	PPV		1/(1 + 1) = 0.50 (0.01–0.99)
	NPV		96/(96 + 2) = 0.98 (0.93–1.00)
Spinal cord compression	Yes	3	0
	No	1	96
	Total	4	96
	Sensitivity		3/4 = 0.75 (0.19–0.99)
	Specificity:		96/96 = 1.00 (0.96–1.00)
	PPV		3/(3 + 0) = 1.00 (0.29–1.00)
	NPV		96/(96 + 1) = 0.99 (0.94–1.00)

Abbreviations: NPV, negative predictive value; PPV, positive predictive value.