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Immunoglobulin subtyping and quantification in direct antiglobulin test: positive haemolysis in an HIV-prevalent setting
  1. Thirosha Chetty1,2,
  2. Nikki Bouwer1,2,
  3. Yuen On Wan3,
  4. Johnny Mahlangu1,2
  1. 1Department of Molecular Medicine and Haematology, University of the Witwatersrand Faculty of Health Sciences, Johannesburg, South Africa
  2. 2Haematology, National Health Laboratory Service, Johannesburg, South Africa
  3. 3Southern Community Laboratories, and Department of Pathology, Dunedin School of Medicine, University of Otago, Dunedin, New Zealand
  1. Correspondence to Dr Thirosha Chetty, Department of Molecular Medicine and Haematology, University of the Witwatersrand Faculty of Health Sciences, Johannesburg 2000, South Africa; thirosha.chetty{at}nhls.ac.za

Abstract

Aims Positive direct antiglobulin tests (DATs) are valuable in identifying the aetiology of autoimmune haemolysis and in guiding therapeutic intervention. However, in HIV-positive individuals with background polyclonal gammopathy, a positive DAT in the absence of haemolysis is common. In this setting, IgG quantification and subtyping may be of value, as this is possible with the recently introduced gel cards. There is paucity of literature evaluating the diagnostic usefulness of IgG subtyping and quantification in HIV-positive individuals who are investigated for autoimmune haemolytic anaemia (AIHA). This study evaluated the usefulness of IgG quantification and subtyping in the diagnostic work-up of AIHA in patients with a positive DAT, with and without HIV infection.

Methods This retrospective, cross-sectional study included patients investigated for AIHA in a quaternary care hospital. Those with a positive DAT had their IgG subtyped and quantified using the ID-Card DAT IgG1/IgG3 and IgG-dilution cards (Bio-Rad, Cressier, Switzerland).

Results Ninety patients admitted from December 2019 to March 2020 were investigated for AIHA. Forty-four (49%) patients had a positive DAT of whom 26 (59%) had evidence of haemolysis, and 16 (36%) were HIV positive. Concurrent HIV and haemolysis were present in eight patients, two of whom had IgG1 although none had an IgG antibody titre >1:30. None of the HIV-positive patients without features of haemolysis had IgG1/IgG3 or IgG antibody titres >1:30.

Conclusion In our clinical setting, IgG quantification and subtyping were found to be of limited value in the diagnostic characterisation of AIHA in HIV-positive patients with false-positive DAT.

  • acquired immunodeficiency syndrome
  • autoantibodies
  • haematology
  • immunoglobulins

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Footnotes

  • Handling editor Mary Frances McMullin.

  • Contributors TC—study design, data collection, data analysis and paper writing. NB, YOW and JM—study design, data analysis, critical review and paper writing. All authors approved the submitted and final version of the manuscript.

  • Funding This work was funded by the National Health Laboratory Service (NHLS) K-project (KNC 180).

  • Competing interests None declared.

  • Patient consent for publication Not required.

  • Ethics approval This cross-sectional, retrospective study conducted in a quaternary care hospital was reviewed and approved by the Human Research Ethics Committee of the University of the Witwatersrand.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data availability statement Data are available upon reasonable request.

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