TPHA

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The TPHA (Treponema Pallidum Haemagglutination Assay) is a test for infection with the syphilis pathogen , Treponema pallidum. In TPHA, indirect detection is carried out by examining the patient's serum for antibodies .

principle

One takes erythrocytes (red blood cells), the surface with proteins and polysaccharides of Treponema pallidum has been coated. Then patient serum is added. If the patient's serum contains antibodies against Treponema pallidum , these are sent to the above. Binding proteins or polysaccharides to the erythrocytes and networking them. This cross-linking can be seen with the naked eye as clumping of the erythrocytes (hence the term hemagglutination ). If the patient's serum does not contain antibodies, the erythrocytes will simply sediment . This is also visible macroscopically. The sensitivity of the TPHA is between 86 and 96%, in HIV patients it is 83%.

If this screening test is positive, you do another control attempt with the so-called FTA-Abs test . Further methods are the Venereal Disease Research Laboratory test (VDRL) and the rapid plasma reagin test (RPR).

A false positive test result (in the case of VDRL and RPR, i.e. the "non-treponemal-specific antibody tests") is due, for example, to the antiphospholipid syndrome . The thus formed antiphospholipid antibodies also bind to Cardiolipins the cell membrane of Treponema pallidum . This results in a false positive test result in the form of clumping of the erythrocytes without the need for treponemas.

Individual evidence

  1. ^ W. Krause: [Syphilis]. In: The Urologist. Ed. A. Volume 45, number 12, December 2006, pp. 1494-1500, doi: 10.1007 / s00120-006-1230-4 . PMID 17089143 .
  2. ^ Walter Siegenthaler, André Aeschlimann (ed.): Siegenthaler's differential diagnosis: internal diseases - from symptom to diagnosis . 19., completely reworked. Edition. Thieme, Stuttgart 2005, ISBN 978-3-13-344819-2 , p. 162 ( limited preview in Google Book search).
  3. ↑ a b L. Creegan, HM Bauer, MC Samuel, J. Klausner, S. Liska, G. Bolan: An evaluation of the relative sensitivities of the venereal disease research laboratory test and the Treponema pallidum particle agglutination test among patients diagnosed with primary syphilis. In: Sexually transmitted diseases. Volume 34, Number 12, December 2007, pp. 1016-1018, PMID 18080352 .
  4. ↑ K. Manavi, H. Young, A. McMillan: The sensitivity of syphilis assays in detecting different stages of early syphilis. In: International journal of STD & AIDS. Volume 17, Number 11, November 2006, pp. 768-771, doi: 10.1258 / 095646206778691185 . PMID 17062183 .
  5. ↑ V. Wiwanitkit: A cost-utility analysis of Treponema pallidum haemagglutination (TPHA) testing for syphilis screening of blood donors: is the TPHA test useful for syphilis screening in a blood center? In: Blood transfusion = Trasfusione del sangue. Volume 7, number 1, January 2009, pp. 65-66, doi: 10.2450 / 2008.0024-08 . PMID 19290082 . PMC 2652238 (free full text).
  6. ↑ Diagnosis and therapy of syphilis update S2k 2019. Accessed on June 6, 2020 .