Table 2 

Contingency management intervention metrics 

Metric^{a} 
Participants (n = 70)^{b} 


% Visits attended, mean (SD); median (IQR) 
37 (1.4); 25 (854) 
% Visits attended, n (%) 

0% 
4 (6) 
125% 
32 (46) 
2650% 
15 (21) 
5175% 
10 (14) 
7599% 
6 (9) 
100% 
3 (4) 
% Metabolitefree urine samples out of those attended, mean (SD); median (IQR) 
75 (3.6); 85 (0.51.0) 
% Metabolitefree urine samples out of total possible visits, mean (SD); median (IQR)^{b} 
29 (1.3); 18 (842) 
% Metabolitefree urine samples, n (%)^{c} 

0% 
7 (10) 
125% 
37 (53) 
2650% 
13 (19) 
5175% 
5 (7) 
7599% 
6 (9) 
100% 
2 (3) 
Number of continuous metabolitefree samples, mean (SD); median (IQR)^{c} 
4.2 (5.5); 2 (15) 
Number of continuous metabolitefree samples, n (%)^{c} 

Never submitted a metabolitefree sample 
7 (10) 
Submitted only single, nonconsecutive metabolitefree samples 
25 (36) 
28 
28 (40) 
912 
4 (6) 
1324 
6 (9) 
Earnings, US$ mean (SD); median (IQR) 
112 (138); 50 (15150) 


IQR, interquartile range; SD, standard deviation. ^{a}Data are n (%) unless otherwise noted. ^{b}63 participants had 24 possible visits, 5 participants had 36 possible visits, 1 participant had 33 possible visits, and 1 participant had 25 possible visits (mean = 25 visits). ^{c}We assumed that during visits the participant did not attend, he would have submitted a urine sample positive for methamphetamine or cocaine metabolites. 

Menza et al. BMC Public Health 2010 10:774 doi:10.1186/1471245810774 