Internal quality assurance in diagnostic microbiology: A simple approach for insightful data
Straight line represents the line of identity, expressing perfect match. Pointed lines delaminate a ± 3.3 Ct tolerance margin. Represented are low positive versus negative results (n = 5, diamonds); moderate positive versus negative results (n = 1, square), quantitative discrepancies with over one log10 difference in copies/ml (straight triangles, n = 3), quantitative discrepancy with difference over 3.3Ct but less than one log10 (reversed triangle, n = 1); agreeing positive results (rounds, n = 20). 92 negative agreeing results are not represented on this figure. Note that these results here include two negative pairs and one positive pair of tests that were not quantitatively reported in copies/ml but only reported in Ct number by the laboratory.