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):
  • primary: 69-90%
  • secondary: 100%
  • 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

More general terms

• treponemal serologic test for syphilis

Additional terms

• syphilis
• Treponema pallidum