The agreement chart as an alternative to the receiver-operating characteristic curve for diagnostic tests.
OBJECTIVE
For diagnostic tests, the most common graphical representation of the information is the receiver-operating characteristic (ROC) curve. The "agreement chart" displays the information of two observers independently classifying the same n items into the same k categories, and can be used if one considers one of the "observers" as the diagnostic test and the other as the known outcome. This study compares the two charts and their ability to visually portray the various relevant summary statistics that assess how good a diagnostic test may be, such as sensitivity, specificity, predictive values, and likelihood ratios.


METHODS
The geometric relationships displayed in the charts are first described. The relationship between the two graphical representations and various summary statistics is illustrated using data from three common epidemiologically relevant health issues: coronary heart disease, screening for breast cancer, and screening for tuberculosis.


RESULTS
Whereas the ROC curve incorporates information on sensitivity and specificity, the agreement chart includes information on the positive and negative predictive values of the diagnostic test.


CONCLUSIONS
The agreement chart should be considered as an alternative visual representation to the ROC for diagnostic tests.
Bangdiwala
Shrikant I
SI
University of North Carolina, 137 E. Franklin Street, Chapel Hill, NC 27514, USA. kant@unc.edu
Haedo
Ana S
AS
Natal
Marcela L
ML
Villaveces
Andrés
A
D019540:Area Under Curve; D001943:Breast Neoplasms / Q000175:diagnosis* / Q000453:epidemiology; D003327:Coronary Disease / Q000175:diagnosis* / Q000453:epidemiology; D003955:Diagnostic Tests, Routine / Q000379:methods*; D005189:False Positive Reactions; D005260:Female; D006801:Humans; D008403:Mass Screening; D015233:Models, Statistical; D015588:Observer Variation; D012372:ROC Curve; D012680:Sensitivity and Specificity; D014376:Tuberculosis / Q000175:diagnosis* / Q000453:epidemiology