Diagnostic Challenges on the Laboratory Detection of Lupus Anticoagulant

Association Between Novel Antiphospholipid Antibodies and Adverse Pregnancy Outcomes

OBJECTIVE

To investigate the value of anti-β2 glycoprotein-I domain 1 (aD1) and antiphosphatidylserine-prothrombin antibodies for predicting adverse pregnancy outcomes in an at-risk population and to describe the relationship among aD1, antiphosphatidylserine-prothrombin, lupus anticoagulant, and other antiphospholipid antibodies (aPL).

METHODS

Data were obtained from a prospective cohort of pregnant patients with aPL, with systemic lupus erythematosus (SLE) (n=59) or without SLE (n=106), or SLE without aPL (n=100) (PROMISSE [Predictors of Pregnancy Outcome in Systemic Lupus Erythematosus and Antiphospholipid Syndrome] study; NCT00198068). Levels of aD1 and antiphosphatidylserine-prothrombin were quantified with the QUANTA Flash and QUANTA Lite systems, respectively, in sera collected at less than 18 weeks of gestation. Adverse pregnancy outcome was defined as delivery at before 34 weeks of gestation for preeclampsia or placental insufficiency or fetal death after 12 weeks of gestation. Receiver operating characteristic (ROC) analysis assessed the diagnostic properties of aD1 and antiphosphatidylserine-prothrombin for adverse pregnancy outcomes. Bivariate comparisons were made between each biomarker. Multivariable regression modeling of adverse pregnancy outcomes was performed, and backward selection determined variables for a final model for adverse pregnancy outcomes. Logistic regression of lupus anticoagulant quantified the association with aD1 and antiphosphatidylserine-prothrombin. The rate of adverse pregnancy outcomes was described by combined results of lupus anticoagulant, aD1, and antiphosphatidylserine-prothrombin immunoglobulin G (IgG).

RESULTS

Of 265 individuals, 45 (17.0%) experienced adverse pregnancy outcomes. Area under the curve from ROC analysis for aD1 was 0.734 (95% CI, 0.664-0.805), for antiphosphatidylserine-prothrombin IgG was 0.83 (95% CI, 0.751-0.899), and for antiphosphatidylserine-prothrombin immunoglobulin M (IgM) was 0.612 (95% CI, 0.520-0.703). Markers associated with adverse pregnancy outcomes were aD1 (P<.001), anticardiolipin IgG (P<.001), β2-glycoprotein I IgG (P=.003), antiphosphatidylserine-prothrombin IgG (P<.001), antiphosphatidylserine-prothrombin IgM (P=.03), and lupus anticoagulant (P<.001). Backward selection identified lupus anticoagulant, aD1, and antiphosphatidylserine-prothrombin IgG for final adverse pregnancy outcome modeling: lupus anticoagulant odds ratio (OR) 7.0 (95% CI, 3.4-14.4), aD1 OR 12.1 (95% CI, 3.64-40.2), and antiphosphatidylserine-prothrombin IgG OR 11.4 (95% CI, 5.2-25.2). Both aD1 and antiphosphatidylserine-prothrombin IgG remained significant when lupus anticoagulant was removed from the model. Both aD1 and antiphosphatidylserine-prothrombin IgG performed the best in ruling in adverse pregnancy outcomes. With a likelihood ratio less than 0.1, aD1 or antiphosphatidylserine-prothrombin IgG performed well for ruling out adverse pregnancy outcomes. Both aD1 and antiphosphatidylserine-prothrombin IgG were associated with lupus anticoagulant positivity: OR 27.9 (95% CI, 12.1-64.0) if both were positive. Adverse pregnancy outcomes were highest in those with positive lupus anticoagulant, aD1, and antiphosphatidylserine-prothrombin IgG (47.6%).

CONCLUSION

In pregnant individuals with aPL, with or without SLE, aD1 and antiphosphatidylserine-prothrombin IgG are significant independent predictors of adverse pregnancy outcomes and are strongly associated with lupus anticoagulant. Combined use may identify patients at greatest risk for severe obstetric complications.

Antiphospholipid antibodies in patients with antiphospholipid syndrome

Antiphospholipid syndrome (APS) is a rare systemic autoimmune disease characterized by recurrent pregnancy morbidity or thrombosis in combination with the persistent presence of antiphospholipid antibodies (aPLs) in plasma/serum. Antiphospholipid antibodies are a heterogeneous, overlapping group of autoantibodies, of which anti-β2-glycoprotein I (aβ2GPI), anticardiolipin (aCL) antibodies and antibodies that prolong plasma clotting time in tests in vitro known as lupus anticoagulant (LAC) are included in the laboratory criteria for the diagnosis of APS. The presence of LAC antibodies in plasma is indirectly determined by measuring the length of coagulation in two tests - activated partial thromboplastin time (aPTT) and diluted Russell's viper venom time (dRVVT). The concentration of aβ2GPI and aCL (immunglobulin G (IgG) and immunoglobulin M (IgM) isotypes) in serum is directly determined by solid-phase immunoassays, either by enzyme-linked immunosorbent assay (ELISA), fluoroimmunoassay (FIA), immunochemiluminescence (CLIA) or multiplex flow immunoassay (MFIA). For patient safety, it is extremely important to control all three phases of laboratory testing, i.e. preanalytical, analytical and postanalytical phase. Specialists in laboratory medicine must be aware of interferences in all three phases of laboratory testing, in order to minimize these interferences. The aim of this review was to show the current pathophysiological aspects of APS, the importance of determining aPLs-a in plasma/serum, with an emphasis on possible interferences that should be taken into account when interpreting laboratory findings.

Cardiac involvement in the catastrophic antiphospholipid syndrome (CAPS): Lessons from the "CAPS registry"

OBJECTIVE

To analyze the demographic, clinical, and laboratory characteristics of catastrophic antiphospholipid syndrome (CAPS) patients with cardiac involvement, and to identify the factors associated with this cardiac involvement.

MATERIAL AND METHODS

Based on the analysis of the "CAPS Registry", the demographic, clinical, and serological characteristics of patients with cardiac involvement were analyzed. Cardiac involvement was defined as heart failure, valvular disease, acute myocardial infarction, pericardial effusion, pulmonary arterial hypertension, systolic dysfunction, intracardiac thrombosis, and microvascular disease. Univariate and multivariate analysis was used for multiple comparisons.

RESULTS

749 patients (293 [39 %] women and mean age 38.1 ± 16.2 years) accounting for 778 CAPS events were included, of them 404 (52 %) had cardiac involvement. The main cardiac manifestations were heart failure in 185/377 (55 %), valve disease in 116/377 (31 %), and acute myocardial infarction in 104/378 (28 %). Of 58 patients with autopsy/biopsy, 48 (83 %) had cardiac thrombotic microangiopathy, Stroke (29% vs. 21 %, p = 0.012), transient cerebral vascular accident (2% vs. 1 %, p = 0.005), pulmonary infarction (26% vs. 3 %, p = 0.017), renal infarction (46% vs. 35 %, p = 0.006), acute kidney injury (70% vs. 53 %, p < 0.001), and livedo reticularis (24% vs. 17 %, p = 0.016) were significantly more frequent during CAPS events with versus without heart involvement. Multivariate analysis identified acute kidney injury (OR 1.068, IC 95 % 1.8-4.8, p < 0.001) as the only clinical characteristics that were, independently, associated with cardiac involvement in CAPS events. Cardiac involvement was not related to higher mortality.

CONCLUSIONS

Cardiac involvement is frequent in CAPS, with association with kidney involvement, and it is not related to higher mortality. The presence of cardiac microthrombosis was demonstrated in most biopsies/autopsies performed.

Lupus Anticoagulant Detection under the Magnifying Glass

Diagnosis of antiphospholipid syndrome (APS) requires the presence of a clinical criterion (thrombosis and/or pregnancy morbidity), combined with persistently circulating antiphospholipid antibodies (aPL). Lupus anticoagulant (LA) is one of the three laboratory parameters (the others being antibodies to either cardiolipin or β2-glycoprotein I) that defines this rare but potentially devastating condition. For the search for aCL and aβ2-GP-I, traditionally measured with immunological solid-phase assays (ELISA), several different assays and detection techniques are currently available, thus making these tests relatively reliable and widespread. On the other hand, LA detection is based on functional coagulation procedures that are characterized by poor standardization, difficulties in interpreting the results, and interference by several drugs commonly used in the clinical settings in which LA search is appropriate. This article aims to review the current state of the art and the challenges that clinicians and laboratories incur in the detection of LA.

Direct oral anticoagulant adsorption and laboratory detection of lupus anticoagulant

Direct oral anticoagulants (DOACs) interfere with many coagulation assays, mostly in lupus anticoagulant (LA) detection, causing false positive and negative results. Despite guidelines recommendations, LA testing may be important during anticoagulation when the clinician has to decide whether to prolong or discontinue the drug.

OBJECTIVES

In this study, the effect of activated charcoal (DOAC-Stop, DS) as a DOAC-adsorbent was investigated on samples from DOACs treated and untreated patients.

BASIC METHODS

165 plasma samples with a LA request were collected in three laboratories: 105 were from patients receiving DOACs and 60 were from nonanticoagulated patients with 30 LA negative and 30 LA positive. All coagulation screening assays and LA assays were evaluated before and after DS treatment.

RESULTS

The adsorption technique reduced DOACs concentration below the Lower Limit of Quantification. For nonanticoagulated patients: no significant difference in ratio results of coagulation screening (prothrombin time, activated partial thromboplastin time and thrombin time) and LA tests were observed before and after addition of DS in LA positive and negative patients. Every LA was correctly classified. For anticoagulated patients: a statistically significant difference was found for coagulation screening assays and LA assays. Final LA conclusions changed after DS addition from positive to negative in 58.9% of patients (more frequently with Rivaroxaban) and from negative to positive in 8% of patients (more frequently with Apixaban).

CONCLUSIONS

Our study suggests that DOAC-Stop can be used in daily laboratory practice to remove DOACs interference for a more accurate assessment of LA that is essential for diagnosis and management of APS patients.

Added value of antiphosphatidylserine/prothrombin antibodies in the workup of thrombotic antiphospholipid syndrome: Communication from the ISTH SSC Subcommittee on Lupus Anticoagulant/Antiphospholipid Antibodies

BACKGROUND

Diagnosis of antiphospholipid syndrome (APS) requires persistent presence of lupus anticoagulant (LAC), anticardiolipin (aCL) IgG/IgM, or anti-β2 glycoprotein I (aβ2GPI) IgG/IgM antibodies. Other antiphospholipid antibodies (aPL) such as antiphosphatidylserine/prothrombin antibodies (aPS/PT) are promising in assessment of thrombotic APS (TAPS).

AIM

To evaluate the added value of aPS/PT IgG and IgM in TAPS.

MATERIAL AND METHODS

aPS/PT IgG/IgM, aCL IgG/IgM, aβ2GPI IgG/IgM, and LAC were determined in 757 patients (TAPS and controls). aPS/PT cut-off values were calculated, and aPS/PT titers and positivity were compared between TAPS and controls, type of thrombosis, and antibody profiles. Likelihood ratios (LR), odds ratios (OR), and aPL score were determined.

RESULTS

aPS/PT IgG and IgM were associated with TAPS and triple positivity. In-house calculated cut-offs were higher for IgM (43 units), compared to manufacturer's cut-off (30 units). Thresholds of 90 (IgG) and 200 (IgM) units were determined as high-titer cut-off. Higher aPS/PT titers were observed in triple positive patients and showed higher LR and OR for TAPS. aPS/PT was independently associated with TAPS when adjusted for aCL/aβ2GPI, but not when adjusted for LAC. In isolated LAC positive patients, aPS/PT was positive in 27.1% TAPS patients and in 77.3% patients with autoimmune disease. Diagnostic value of aPL score did not differ with and without including aPS/PT.

CONCLUSION

aPS/PT positivity, especially with high antibody titer, is associated with TAPS diagnosis. Analysis on top of current laboratory criteria is not essential in TAPS diagnosis, but aPS/PT could be useful in patients with thrombosis and a double positive aPL profile (aCL+/aβ2GPI+).