Aetiological factors related to a positive direct antiglobulin test result in human immunodeficiency virus-infected patients

A Study of Clinical and Serological Correlation of Positive Direct Antiglobulin Test in Blood Bank at a Tertiary Care Center

Objectives  Detection of red cell bound immunoglobulins and/or complement by direct antiglobulin test (DAT) is a crucial serological assay in the diagnosis of autoimmune hemolytic anemia (AIHA). However, DAT may be positive in a variety of clinical conditions with or without hemolysis. We aimed at evaluating the clinical and serological correlation of positive DAT by categorizing the clinical conditions associated with positive DAT, estimating the presence of in vivo hemolysis in case of positive DAT with polyspecific and monospecific antisera and correlating the strength of positive DAT with the presence of hemolysis.

Materials and Methods  The prospective observational study was performed on 200 samples that were positive for DAT with polyspecific antiglobulin reagent as the baseline investigation. These samples were further tested with anti-immunoglobulin G and anti-C3 monospecific DAT reagents to evaluate the type of protein responsible for positive DAT. The antiglobulin tests were performed by tube technique. DAT positivity was graded (1+ to 4 + ) in each patient. Autocontrol test was included. The patients with positive polyspecific DAT were categorized into different clinical conditions. The presence or absence of in vivo hemolysis was evaluated in all clinical categories and also for each grade of positivity with polyspecific and monospecific antiglobulin reagents.

Statistical Analysis  Binomial logistic regression and Mann–Whitney U test were applied to between the group analyses. For categorical variables, Fisher's exact test and relative risk were used. The qualitative data were expressed in numbers and percentages.

Results  The highest number of patients (75/200, 37.5%) belonged to the autoimmune diseases group. Tuberculosis and hepatitis C were the main infectious diseases associated with positive DAT. Out of 200 DAT-positive patients, 98 (49%) had in vivo hemolysis and 102 (51%) did not have hemolysis. AIHA (22) and systemic lupus erythematosus (18) were the commonest clinical conditions associated with in vivo hemolysis. All the 11 samples that showed positivity with only anti-C3 reagent did not show any hemolysis. There was statistically significant increase in the incidence of in vivo hemolysis with increasing grades of DAT positivity with all the three antihuman globulin reagents.

Conclusion  There are different disease conditions which show positive DAT with or without hemolysis. So, it is important to clinically and serologically correlate positive DAT results.

Low hemoglobin levels are associated with direct antiglobulin test positivity in patients with acute-on-chronic liver failure

BACKGROUND

Multiple factors contribute to anemia in patients with Hepatitis B virus (HBV)related acute-on-chronic liver failure (ACLF); however, the mechanism is unclear. The purpose of this study was to evaluate the clinical significance of the direct antiglobulin test (DAT) in patients with HBV related ACLF.

METHODS

DAT was used to detect immunoglobulins and/or complement proteins on the surface of erythrocytes.

RESULTS

We recruited 78 HBV-associated ACLF patients, 30 chronic hepatitis B(CHB)patients and 40 healthy people between October 2015 and May 2016. In HBV related ACLF patients, the hemoglobin concentration, number of erythrocytes, and hematocrit value were significantly lower, while the erythrocyte distribution width was significantly higher, compared to patients with CHB and healthy controls (HCs) (P < 0.001). The rates of DAT positivity in HBV related ACLF patients, CHB patients, and HCs were 62.8 %, 13.3 %, and 0%, respectively. DAT-positive ACLF patients exhibited lower Hb levels, older average age, as well as higher total bilirubin, alanine aminotransferase, and complement component 3 levels compared to DAT-negative patients.

CONCLUSIONS

HBV related ACLF patients showed significant alterations in erythrocyte parameters, possibly reflecting disease development and severity. The high presence of erythrocyte autoantibodies suggested that immunologic clearance of erythrocytes contributed to multifactorial anemia in HBV related ACLF patients.

Immunoglobulin subtyping and quantification in direct antiglobulin test: positive haemolysis in an HIV-prevalent setting

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.

Autoantibody-Mediated Erythrophagocytosis Increases Tuberculosis Susceptibility in HIV Patients

Macrophage dysfunction is associated with increased tuberculosis (TB) susceptibility in patients with human immunodeficiency virus (HIV) infection. However, the mechanisms underlying how HIV infection impairs macrophage function are unclear. Here, we found that levels of autoantibodies against red blood cells (RBCs) were significantly elevated in patients with HIV as determined by direct antiglobulin test (DAT). DAT positivity was significantly associated with TB incidence in both univariate and multivariate analyses (odds ratio [OR] = 11.96 [confidence interval {CI}, 4.68 to 30.93] and 12.65 [3.33 to 52.75], respectively). Ex vivo analysis showed that autoantibodies against RBCs enhanced erythrophagocytosis and thus significantly impaired macrophage bactericidal function against intracellular Mycobacterium tuberculosis Mechanistically, autoantibody-mediated erythrophagocytosis increased heme oxygenase-1 (HO-1) expression, which inhibited M. tuberculosis-induced autophagy in macrophages. Silencing ATG5, a key component for autophagy, completely abrogated the effect of erythrophagocytosis on macrophage bactericidal activity against M. tuberculosis In conclusion, we have demonstrated that HIV infection increases autoantibody-mediated erythrophagocytosis. This process impairs macrophage bactericidal activity against M. tuberculosis by inhibiting HO-1-associated autophagy. These findings reveal a novel mechanism as to how HIV infection increases TB susceptibility.IMPORTANCE HIV infection significantly increases TB susceptibility due to CD4 T-cell loss and macrophage dysfunction. Although it is relatively clear that CD4 T-cell loss represents a direct effect of HIV infection, the mechanism underlying how HIV infection dampens macrophage function is unknown. Here, we show that HIV infection enhances autoantibody-mediated erythrophagocytosis, which dampens macrophage bactericidal activity against TB by inhibiting HO-1-associated autophagy. Our findings reveal a novel mechanism explaining how HIV infection increases susceptibility to TB. We propose that DAT could be a potential measure to identify HIV patients who are at high TB risk and who would be suitable for anti-TB chemotherapy preventive treatment.