As discussed in [6], the methods that have been used on many
bioassay studies, including modifications of the original protocols
and variations in the way in which the results were interpreted,
complicates cross study comparisons. The changes in the WHO
guidelines (i.e. revised diagnostic doses), the absence of standard
diagnostic doses for some insecticides (for example, different concentrations
/ exposure times used across studies for fenitrothion)
and the independent determination of diagnostic dose in some
cases (following determination of the dose response of a susceptible
strain from the region) all contribute to large discrepancies in
the methodologies (Table 1). Thus, the data among different studies
cannot be easily compared, particularly if they were summarized
as Resistant Ratios (RR). Presentation of actual LC50 or
exposure time/mortality values is therefore preferable (Table 1).