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. Author manuscript; available in PMC: 2014 Jul 2.
Published in final edited form as: Anal Chem. 2013 Jun 18;85(13):6453–6460. doi: 10.1021/ac400989p

Figure 3.

Figure 3

Validation standards used by readers for the analysis of PAD colorimetric results. Tests with binary or ternary outcomes are compiled into a small color key. Lane test reagents are copper sulfate (i), ninhydrin (ii), nitroaniline (iii), iron (III) chloride (iv), tri-iodide (v), eosine red (vi) and cobalt thiocyanate (a). Tests of the TB PAD present a more complex array of results and are evaluated using the “fringe” diagram. Represented here is a portion of the fringe diagram for the copper sulfate test for ethambutol, lane B of the TB PAD (b). The “fringe” diagram is a collection of outcomes from testing different quantities of all 15 combinations of the four main TB drugs, plus a library of excipients and substitute APIs. The reader matches each lane of the PAD to the most similar group of images to identify analytes present. See See Figure S2, Supporting Information, for the complete fringe diagram.