Standardisation of disk diffusion results for antibiotic susceptibility testing using the sirscan automated zone reader

Table 2 Relative deviation of zone diameter values and resulting discrepancies of the Sirscan (on-screen adjusted) and manual calliper measurements

	Relative deviation of zone diameters values			Discrepancies
	(% of all measurements)			(% of all Sirscan measurements)
	Sirscan < calliper	Sirscan = calliper	Sirscan > calliper	minor	major	very major
Gram-negative rods	19	45	36	1.27	0	0
Staphylococcus spp.	27	37	36	0.94	0	0
Enterococcus spp.	53	35	12	0	0	0

For discrepancy analysis manual calliper measurements were regarded as the gold standard. Sirscan values were on-screen adjusted by an experienced person as recommended by the manufacturer.

ISSN: 1471-2180