Drug-Resistant Malaria - libdoc.who.int - World Health Organization

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TABLE 3~ Comparison of in vivo and in vitro
Results of Chloroquine Sensitivity
Testing, Papua-New Guinea
In v~vo resul t s
In vitro tests
(critical con- Children below 10 years Chi ldren 10 years of age
centration in of age (87) and over (122)
nanomols)
S RI RII/III S RI RH/Ill
Less than 1.0 28 0 0 47 0 0
1.0 or 1. 25 4 4 0 2 6 0
1.5 and above 7 35 9 19 40 8
study was undertaken using both in vivo and macro in vitro
methods. It showed chloroquine resistance to be geographically
widespread throughout most of the country and at all clinical
levels. Among 226 parallel tests carried out, III showed resistance
in vivo and 115 a sensitive response, as against 143 cases of
resistance in vitro, and 83 sensitive isolates. These results
show a considerable degree of correlation between the two methods
but with a number of "false" resistant cases in the in vitro
tests. This finding may be at least in part explained by the high
degree of immunity prevailing among the schoolchildren included in
these studies, as there are indications that the discrepancy in
the test results increased with age (see Table 3).
Of 32 cases tested in vitro only, 28 were found resistant; of
102 others tested in vivo only, 56 were found resistant. In 1981,
33 tests conducted concurrently in Central Province showed 28
cases resistant in vitro against 20 in vivo. Twenty others tested
in vitro only, were all resistant; 8 others tested in vivo only,
showed 4 sensitive and 4 resistant (RI) responses to chloroquine.
(f) Philippines. Investigations started in 1974 and were
conducted by the Central Headquarters team, Manila, using
comparati ve in vivo and in vit ro tests on the same infec t ions in
preliminary investigations. Patients were residents of Manila,
where malaria transmission is almost unknown. A total of 27 in
vitro and in vivo tests on the same infections were carried out
and an in vivo 28-day follow-up completed ~n the absence of