Table 3 Key requirements for the design and validation of PBACs

• Towel and tampon scores must be validated against the AH method

• Scores must be validated for specific towel/tampon brands and for each absorbency category shown on the chart

• To prevent mis-scoring or confusion, there must be clear visual differences between successive icons

• To assess reproducibility during validation, icon scores should be subjected to repeated testing by different women

• The chart must be validated for all levels of MBL (low, normal and high)

• The method should be able to detect clinically relevant differences in MBL following treatment

• The chart design should be simple, straightforward and user friendly, and patients should be thoroughly briefed in its use, particularly in the interpretation of nonstandard staining patterns

• After validation, the format, size and appearance of the chart should not be changed because this may alter a woman’s perception of scoring

• A paper-based version should be conveniently sized and of robust construction. If an electronic version is used, women should be aware of the protocol in cases of data transmission failure