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Table 4 Results from Dirofilaria immitis (Di) antigen (Ag) and microfilariae (MF) tests on dogs for naturally occurring heartworm infection. In each study listed, microfilariae were confirmed as Dirofilaria immitis by acid phosphatase stain or by PCR unless otherwise noted

From: Prime detection of Dirofilaria immitis: understanding the influence of blocked antigen on heartworm test performance

No. of dogs (% positive)a Di Ag + Di MF +
(%)
Di Ag + Di MF -
(%)
Di Ag - Di MF +
(%)
Di Ag - Di MF -
(%)
Reference
630 (16.2)b 42 (6.7) 23 (3.7) 37 (5.9)b 555 (88.1) [13]
696 (15.1) 49 (7.0) 16 (2.3) 41 (5.9) 591 (84.9) [14]
304 (27.3) 56 (18.4) 22 (7.2) 5 (1.6) 221 (72.7) [15]
24 (62.5) 6 (25.0) 4 (16.7) 5 (20.8) 9 (37.5) [16]
404 (12.1) 21 (5.2) 25 (6.2) 3 (0.7) 355 (87.9) [24]
616 (7.6) 24 (3.9)c 21 (3.4) 2 (0.3)b, c 569 (92.4) [31]
104 (18.3) 13 (12.5) 5 (4.8) 1 (1.0) 85 (81.7) [58]
  1. aPositive for Dirofilaria immitis by at least one laboratory method
  2. bInferred from text description of reported results and prior to heat treatment of samples
  3. cMicrofilariae identified by morphology alone