microhemagglutination Treponema pallidum test; Treponema pallidum particle agglutination test (MHA-TP, TTPA)

Indications: - confirmatory testing for syphilis Principle: - treponemal serologic tests used in the diagnosis of syphilis include: - fluorescent treponemal antibody absorption test (FTA) - microhemagglutination Treponema pallidum test (MHA-TP) - TP-PA indirect fluorescent antibody - these tests are based upon detection of treponemal antigens Clinical significance: - Sensitivity (serum): a) primary: 69-90% b) secondary: 100% c) tertiary: 94% Methods: - in the MHA-TP, heated serum is mixed with a sonicate of non pathogenic Reiter treponemes to remove non-specific antibodies & incubated with sheep erythrocytes coated with sonicated Treponema pallidum in a microtiter plate - if antibodies to Treponema pallidum are present, they react with the sensitized erythrocytes to produce a uniformly thin mat of agglutinated cells that covers the entire bottom of the well - if antibodies are absent, the erythrocytes settle as a smooth ring or button at the bottom of the well - in general the MHA-TP is preferred over the FTA because it is technically less difficult, easier to interpret, & less expensive

Related

syphilis Treponema pallidum

References

Clinical Diagnosis & Management by Laboratory Methods, 19th edition, J.B. Henry (ed), W.B. Saunders Co., Philadelphia, PA. 1996, pg 1186