Table 4. Accuracy of radiation coding in SEER-Medicare registries compared to the Florida, New York, and Texas Registries^*.

Registry	Under- ascertainment	Kappa	Specificity	NPV	PPV
SEER Registries	18.7%	78.6%	97.1%	84.2%	96.5%
Registry 1	5.6%	88.6%	94.3%	93.8%	94.8%
Registry 2	6.3%	93.5%	99.2%	95.5%	98.9%
Registry 3	9.9%	85.7%	95.9%	89.7%	96.0%
Registry 4	12.4%	83.8%	96.9%	87.1%	97.0%
Registry 5	13.3%	78.3%	92.8%	83.7%	94.2%
Registry 6	14.2%	81.7%	96.2%	86.3%	96.1%
Registry 7	16.3%	83.2%	97.7%	90.1%	96.0%
Registry 8	19.8%	78.8%	97.8%	84.9%	97.0%
Registry 9	20.3%	78.6%	98.5%	83.7%	98.0%
Registry 10	21.0%	74.8%	97.1%	79.6%	97.0%
Registry 11	21.4%	73.2%	97.2%	76.9%	97.5%
Registry 12	21.6%	75.4%	96.5%	82.8%	95.4%
Registry 13	23.7%	80.6%	100.0%	88.4%	100.0%
Registry 14	24.7%	75.4%	97.9%	84.3%	96.4%
Registry 15	26.8%	68.3%	96.0%	76.3%	95.4%
Registry 16	27.4%	74.7%	99.1%	83.7%	98.4%
Non-SEER Registries
New York	18.9%	76.6%	95.9%	82.5%	95.5%
Texas	43.9%	55.5%	97.7%	72.3%	95.5%
Florida	51.6%	43.0%	98.2%	58.8%	97.3%

Abbreviations: SEER, Surveillance, Epidemiology and End Results; BCS, breast-conserving surgery; CI, confidence interval; NPV, negative predictive value; PPV, positive predictive value Note: Names of SEER registries are suppressed in according with our Data User’s Agreement to protect confidentiality of individual SEER registries.

^*Specificity, positive predictive value, negative predictive value, and cohen’s kappa statistic were calculated for radiation therapy (RT) receipt coded by registries compared to the gold standard of Medicare billing claims. Underascertainment of RT receipt was defined as the number of cases where Medicare claims indicated that the patient received RT but registry data indicated that the patient did not receive RT, divided by the total number of cases where Medicare claims indicated that the patient received RT (1-sensitivity).