ABSTRACT
BACKGROUND: The PLASMIC score was developed for distinguishing thrombotic thrombocytopenic purpura (TTP) from other types of thrombotic microangiopathy. However, two components of the PLASMIC score, mean corpuscular volume (MCV) and international normalized ratio (INR), showed non-significant differences between TTP and non-TTP patients in previous validations. Here, we validate the PLASMIC score and aim to modify it by adjusting the criteria of MCV and INR. MATERIALS AND METHODS: A retrospective validation of suspected TTP patients was performed by reviewing electronic medical records from two medical centers in Taiwan. The performance of different modified types of the PLASMIC score was carried out. RESULTS: Among 50 patients included in the final analysis, 12 were diagnosed with TTP based on deficiency of ADAMTS13 activity and clinical judgement. When stratified by high (score ≥ 6) and low-intermediate risk (score < 6), the positive predictive value (PPV) of the PLASMIC score to predict TTP was 0.45 (95% confidence interval [CI]: 0.29-0.61). The area under curve (AUC) was 0.70 (95% CI: 0.56-0.82). When adjusting the criteria of the PLASMIC score from MCV < 90 fL to MCV ≥ 90 fL, the PPV increased to 0.57 (95% CI: 0.37-0.75). The AUC was 0.75 (95% CI: 0.61-0.87). When adjusting the INR from >1.5 to >1.1, the PPV increased to 0.56 (95% CI: 0.39-0.71). The AUC was 0.81 (95% CI: 0.68-0.90). CONCLUSION: MCV ≥ 90 fL and/or INR > 1.1 might be suitable modifications for PLASMIC score but should be validated in a larger sample size.
Subject(s)
Purpura, Thrombotic Thrombocytopenic , Thrombotic Microangiopathies , Humans , Purpura, Thrombotic Thrombocytopenic/diagnosis , International Normalized Ratio , Retrospective Studies , Erythrocyte Indices , Thrombotic Microangiopathies/diagnosis , ADAMTS13 ProteinSubject(s)
Acanthocytes/metabolism , Amino Acid Transport Systems, Neutral/genetics , Creatine Kinase/blood , Kell Blood-Group System/genetics , Neuroacanthocytosis/blood , Neuroacanthocytosis/genetics , Alleles , Antigens, Bacterial/blood , Antigens, Surface/blood , Asian People , Down-Regulation , Exons , Frameshift Mutation , Humans , Male , Middle Aged , Up-RegulationABSTRACT
Daratumumab is a monoclonal immunoglobulin against CD38 and has been approved for treating patients with refractory multiple myeloma. The presence of daratumumab in the sera can interfere with pretransfusion testing due to the weakly expression of CD38 on red cells. The reactivity could be mistaken as autoantibody (if autocontrol is positive) or alloantibody (if autocontrol is negative). We present a case that demonstrates daratumumab could mimic a high titer low avidity (HTLA) alloantibody. A 34-year-old male patient of refractory myeloma was recruited in phase three clinical trial involving daratumumab. Samples were sent to the blood bank for pretransfusion testing. Without knowledge of patient having used daratumumab, we mistook the reactivity in the patient's sera as an HTLA antibody due to the results of negative autocontrol and high titers of antibody activity. Antibody screen showed a panreactive pattern and the reactivity against screening cells was up to a titer of 1: 1240. The reactivity was weaker against cord cells than adult cells, became weaker against ZZAP-treated cells and became negative against DDT-treated cells. A discussion with attending physician finally revealed the reactivity was due to the interference caused by daratumumab. The case demonstrates good communication is essential in performing pretransfusion testing for patients receiving daratumumab and other new biological regimens that can interfere with compatibility test.
