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Table 2 In vitro sensitivity of Plasmodium falciparum isolates collected during 2006–2007 and 2008–2009 to chloroquine (CQ), quinine (QN), mefloquine (MQ), and artesunate (AS) and their sensitivity classification

From: Four years’ monitoring of in vitro sensitivity and candidate molecular markers of resistance of Plasmodium falciparum to artesunate-mefloquine combination in the Thai-Myanmar border

Drug

Sensitivity classification

Year 2006–2007

Year 2008–2009

% (n)

IC50, nM

% (n)

IC50, nM

AS

All

100 (56)

2.0 (1.5–2.4)

100 (63)

2.0 (1.5–2.5)

Sensitive

60.7 (34)

1.4 (1.3–1.6)

58.7 (37)

1.4 (1.1–1.8)

Declined sensitivity

39.3 (22)

3.1 (2.8–3.3)

41.3 (26)

3.7 (3.2–4.2)

MQ

All

100 (56)

30.4 (18.0–42.7)

100 (63)

28.8 (16.7–41.0)

Sensitive

42.9 (24)

13.8 (11.3–16.3)

41.3 (26)

16.2 (13.2–19.2)

Resistant

57.1 (32)

51.5 (40.3–62.7)

58.3 (37)

58.7 (49.3–68.1)

CQ

All

100 (56)

69.9 (62.8–77.1)

100 (63)

72.3 (65.4–79.2)

Sensitive

1.8 (1)

9.6

Moderate resistant

76.8 (43)

65.9 (59.9–72.0)

69.8 (44)

66.6 (62.3–70.8)

Highly resistant

21.4 (12)

124.3 (108.1–140.6)

30.2 (19)

132.3 (68.1–196.5)

QN

All

100 (56)

236.3 (186.2–286.4)

100 (63)

230.5 (164.8–296.2)

Sensitive

78.6 (44)

223.0 (178.6–267.3)

93.7 (59)

214.9 (150.4–279.4)

Resistant

21.4 (12)

648.9 (606.1–691.6)

6.3 (4)**

593.6 (491.0–696.2)

  1. Data presented as median IC50 (95% CI) and percentage (number).
  2. **Significant lower proportion than isolates collected from 2006–2007 (p = 0.016, Chi–square test).