SPADA at AOAC Annual Meeting 2023

AOAC O FFICIAL M ETHODS OF A NALYSIS (2012)

B IOLOGICAL T HREAT A GENT M ETHOD V ALIDATION G UIDELINES Appendix I, p. 25

ANNEX H Systems Suitability Requirements for Biological Threat Agent Methods

ANNEX G Logarithmic Transformation of Data from Quantitative Method Developer, Independent, and Collaborative Data Quantitative microbacterial count data from experiments spanning multiple dilutions often do not show a Poisson nor a Gaussian statistical distribution. When the underlying physical mechanism allows for “clustering,” typically a logarithmic transformation will normalize the data. Perform a logarithmic transformation on the reported CFU/unit or spores/unit (including any zero results) as follows: Y = log 10 [CFU/unit + (0.1) f ] where f is the reported CFU/unit or spores/unit corresponding to the smallest reportable result, and “unit” is the reported unit of measure (e.g., g, mL, fi lter). Example: ( 1 ) For the control concentration, the CFU/g is reported as “<0.003.” So CFU/unit = 0.0, and Y = log 10 [0.0 + (0.1)(0.003)] = –3.52. ( 2 ) For the low concentration, the CFU/g is 0.042. So Y = log 10 [0.042 + (0.1)(0.003)] = –1.37. ( 3 ) For the high concentration, the CFU/g is 0.231. So Y = log 10 [0.231 + (0.1)(0.003)] = –0.64.

The controls listed in Table H1 shall be embedded in assays as appropriate. Manufacturer must provide written justi fi cation if controls are not appropriate to an assay.

Table H1. Controls Positive control

Success : Control detected at expected levels Failure : Control not detected or at levels outside of the expected range Success : No detections made Failure: Detections made Success: Control detected at expected levels Failure: Control not detected or at levels outside of the expected range

Designed to demonstrate an appropriate test response. Positive control should be included at a low, but easily, detectable concentration, and should monitor the performance of the entire assay. The purpose of using a low concentration of positive control is to avoid contamination of the test sample and/or instrument. Designed to demonstrate that the assay itself does not produce a detection in the absence of the target organism. The purpose of this control is to rule out contamination in the assay or test. Designed to speci fi cally address the impact of a sample or sample matrix on the assay’s ability to detect the target organism.

Single use per sample (or sample set) run

Negative control

Single use per sample (or sample set) run

Inhibition control

Single use per sample run

© 2012 AOAC INTERNATIONAL