Table 3 Advantages and disadvantages of the different approaches for monitoring anti-malarial resistance

In vivo

Relatively easy to standardize

No heavy equipment required

Provides results directly obtained from patients

Provides the evidence required for modifying treatment policies

Helps to define the first line and second line treatment for case management

Can provide required safety data

Confirms association of parasite resistance with in vitro test results (IC₅₀ values) or molecular resistance markers

Logistics constraints (long follow-up with many patients lost to follow up, lack of patients in low transmission settings, expensive)

Potential over-estimation of treatment failures because of: inter-individual variation in pharmacokinetics including poor absorption, rapid elimination (diarrhoea, vomiting) and/or insufficient or poor biotransformation of pro-drugs because of human genetic characteristics; extrinsic factors such as poor patient compliance (if the totality of treatment is provided), incorrect dosage, poor drug quality or poor microscopy

Potential under-estimation of treatment failures because of host factors such as the immunity or poor microscopy

In vitro

Provides the intrinsic parasite susceptibility to the drug without confounding factors such as immunity and pharmacology

Difficult to standardize

Require a special design (concentration and duration) for certain drugs (i.e. RSA, PSA)

Requires good infrastructure and highly trained staff

Results not always associated with therapeutic efficacy

Molecular

Provides direct information on the resistance status of the parasite. When they are validated, their prevalence in a parasite population are often a good indicator of the level of clinical resistance

Can provide useful information on the spread of resistance

Relatively easy to implement

Requires good infrastructure and highly trained staff

Results not always associated with therapeutic efficacy