I am not expertise on your field however I guess when methods get involved with errors, using two or more tests can enhance the validation of the work.

For example in my field although many researchers have used plate count method to analyze the antibacterial properties of membranes, the inhibition zone method may be regraded as an validation to previous method.

I am sorry, because I am not sure my answer hit the nail on the head, however I hope so.

Good Luck!

Dear Ayat AL-Laaeiby

Broth dilution is the most frequent method for antifungal susceptibility testing. Especially CLSI M27-A2 and M38-A3 documents( or newer versions) for both growth phases of fungi are recommended.  E-test or other methods may be simpler to perform, so it is a good question for researchers, can we use other methods instead of broth dilution?

I think this is the reason what they use more than one method.

The test is performed in microdilution plates. The method is based on the

preparation of antifungal agent working solutions in 100 μL volumes per well (with

the addition of an inoculum also in a volume of 100 μL).

The primary objective of in vitro susceptibility testing is to predict the impact of administration of the tested agent on the outcome of infection caused by the tested organism or similar organisms . In this way, antifungal testing is performed for the same reasons that antibacterial testing is performed

The broth serial dilution is the most pronounced and most documented followed by  using micro dilution plats  nowadays using more than one method mostly in may opinion is either to add extra info like using the disk diffusion method (which by the way can give extra data about the daily growth  is to add more confirmation and to add extra credit to the paper  and also each of the method could serve for different parameter  like MIC IN BROTH AND GROWTH RATIOS in disk diffusion so if you try to read the papers again you may find that each method have different goal

Thank you very much for your reply 

Hi! There are many methods for anti fungal susceptibility testing: broth based methodology for yeasts, commercial broth based MIC systems( Candifast etc), NCCLS method for moulds, Etest, other agar based testing methods... Etest MIC values are generally higher than broth dilution methods but E test has been suggested as an alternative for the labour intensive and time consuming broth dilution methods... I think article by JH Rex 2001 will be helpful to you...

www.ncbi.nlm.nih.gov(anti fungal susceptibility testing:practical aspects and current challenges)