Table 1.

Predictive power of thrice weekly urine drug screens during first two weeks of treatment for persistent MA use at EOT^*

MA Positive Screens	SN	SP	PPV	NPV
>=6	29.3	100.0	1	.32
>=5	46.3	92.7	.95	.37
>=4	61.0	78.6	.90	.40
>=3	75.6	71.4	.89	.49
>=2	80.5	57.1	.85	.49
>=1	93.7	42.9	.83	.69

^*ROC analysis assessed number of MA positive/missing urine drug screens to predict MA use at EOT. Bolded is optimal Youden (1950) predictor; SN=sensitivity; SP=specificity; PPV=positive predictive value; NPV=negative predictive value.