The method of array synthesis can also affect sensitivity and specificity. Increasing the probe concentration per spot can increase sensitivity (Cho and Tiedje, 2002; Relógio et al., 2002; Zhou and Thompson, 2002) . However, this may also decrease specificity by decreasing the overall probe signal intensity (Denef et al., 2003) . The choice of array surface can also be important as use of unmodified array slides can decrease background fluorescence thus requiring a lower signal fluorescence for detection (Kumar et al., 2000; Gudnason et al., 2008) .