Simulated cost-effectiveness of a novel precision-guided dosing strategy in adult patients with Crohn's disease initiating infliximab maintenance therapy

BACKGROUND

Patients with Crohn's disease (CD) who lose response to biologics experience reduced quality of life (QoL) and costly hospitalizations. Precision-guided dosing (PGD) provides a comprehensive pharmacokinetic (PK) profile that allows for biologic dosing to be personalized. We analyzed the cost-effectiveness of infliximab (IFX) PGD relative to two other dose intensification strategies (DIS).

METHODS

We developed a hybrid (Markov and decision tree) model of patients with CD who had a clinical response to IFX induction. The analysis had a US payer perspective, a base case time horizon of 5 years, and a 4-week cycle length. There were three IFX dosing comparators: PGD; dose intensification based on symptoms, inflammatory markers, and trough IFX concentration (DIS1); and dose intensification based on symptoms alone (DIS2). Patients that failed IFX initiated ustekinumab, followed by vedolizumab, and conventional therapy. Transition probabilities for IFX were estimated from real-world clinical PK data and interventional clinical trial patient-level data. All other transition probabilities were derived from published randomized clinical trials and cost-effectiveness analyses. Utility values were sourced from previous health technology assessments. Direct costs included biologic acquisition and infusion, surgeries and procedures, conventional therapy, and lab testing. The primary outcomes were incremental cost-effectiveness ratios (ICERs). The robustness of results was assessed via one-way sensitivity, scenario, and probabilistic sensitivity analyses (PSA).

RESULTS

PGD was the cost-effective IFX dosing strategy with an ICER of 122,932 $ per quality-adjusted life year (QALY) relative to DIS1 and dominating DIS2. PGD had the lowest percentage (1.1%) of patients requiring a new biologic through 5 years (8.9% and 74.4% for DIS1 and DIS2, respectively). One-way sensitivity analysis demonstrated that the cost-effectiveness of PGD was most sensitive to the time between IFX doses. PSA demonstrated that joint parameter uncertainty had moderate impact on some results.

CONCLUSIONS

PGD provides clinical and QoL benefits by maintaining remission and avoiding IFX failure; it is the most cost-effective under conservative assumptions.

Corrigendum: Poor prognostic factors of pharmacokinetic origin predict outcomes in inflammatory bowel disease patients treated with anti-tumor necrosis factor-α

[This corrects the article DOI: 10.3389/fimmu.2024.1342477.].

Adalimumab Clearance, Rather Than Trough Level, May Have Greatest Relevance to Crohn's Disease Therapeutic Outcomes Assessed Clinically and Endoscopically

OBJECTIVE

We postulated that adalimumab [ADA] drug clearance [CL] may be a more critical determinant of therapeutic outcome than ADA concentration. This was tested in Crohn's disease [CD] patients undergoing ADA maintenance treatment.

METHODS

CD patients from four cohorts received ADA induction and started maintenance therapy. Therapeutic outcomes consisted of endoscopic remission [ER], sustained C-reactive protein [CRP] based clinical remission [defined as CRP levels below 3 mg/L in the absence of symptoms], and faecal calprotectin [FC] level below 100 µg/g. Serum albumin, ADA concentration, and anti-drug antibody status were determined using immunochemistry and homogeneous mobility shift assay, respectively. CL was determined using a nonlinear mixed effect model with Bayesian priors. Statistical analysis consisted of Mann-Whitney test and logistic regression with calculation of odds ratio. Repeated event analysis was conducted using a nonlinear mixed effect model.

RESULTS

In 237 enrolled patients [median age 40 years, 45% females], median CL was lower in patients achieving ER as compared with those with persistent active endoscopic disease [median 0.247 L/day vs 0.326 L/day, respectively] [p <0.01]. There was no significant difference in ADA concentration between patients in endoscopic remission compared with those with recurrence [median 9.3 µg/mL vs 11.7 µg/mL, respectively]. Sustained CRP-based clinical remission and FC levels below 100 µg/g were generally associated with lower CL and higher ADA concentration. Repeated event analysis confirmed those findings with better performances of CL than concentration in associating with ER and other outcomes.

CONCLUSION

Lower ADA clearance is associated with an improved clinical outcome for patients with Crohn's disease and may be a superior pharmacokinetic measure than concentration.

Poor prognostic factors of pharmacokinetic origin predict outcomes in inflammatory bowel disease patients treated with anti-tumor necrosis factor-α

Introduction

We evaluated baseline Clearance of anti-tumor necrosis factors and human leukocyte antigen variant (HLA DQA1*05) in combination as poor prognostic factors (PPF) of pharmacokinetic (PK) origin impacting immune response (formation of antidrug antibodies) and disease control of inflammatory bowel disease (IBD) patients treated with infliximab or adalimumab.

Methods

Baseline Clearance was estimated in IBD patients before starting treatment using weight and serum albumin concentrations. HLA DQA1*05 carrier status (rs2097432 A/G or G/G variant) was measured using real time polymerase chain reaction. The outcomes consisted of immune response, clinical and biochemical remission (C-reactive protein<3 mg/L in the absence of symptoms), and endoscopic remission (SES-CD<3). Statistical analysis consisted of logistic regression and nonlinear mixed effect models.

Results and discussion

In 415 patients enrolled from 4 different cohorts (median age 27 [IQR: 15-43] years, 46% females), Clearance>0.326 L/day and HLA DQA1*05 carrier status were 2-fold more likely to have antidrug antibodies (OR=2.3, 95%CI: 1.7-3.4; p<0.001, and OR=1.9, 95%CI: 1.4-2.8; p<0.001, respectively). Overall, each incremental PPF of PK origin resulted in a 2-fold (OR=2.16, 95%CI: 1.7-2.7; p<0.11) [corrected] higher likelihood of antidrug antibody formation. The presence of both PPF of PK origin resulted in higher rates of antidrug antibodies (p<0.01) and lower clinical and biochemical remission (p<0.01). Each incremental increase in PPF of PK origin associated with lower likelihood of endoscopic remission (OR=0.4, 95%CI: 0.2-0.7; p<0.001). Prior biologic experience heightened the negative impact of PPF of PK origin on clinical and biochemical remission (p<0.01). Implementation of proactive therapeutic drug monitoring reduced it, particularly during maintenance and in the presence of higher drug concentrations (p<0.001). We conclude that PPF of PK origin, including both higher Clearance and carriage of HLA DQA1*05, impact outcomes in patients with IBD.

Nutritional Biomarkers for the Prediction of Response to Anti-TNF-α Therapy in Crohn's Disease: New Tools for New Approaches

Crohn's disease (CD) is a chronic disorder of the digestive tract characterized by an uncontrolled immune-mediated inflammatory response in genetically predisposed individuals exposed to environmental risk factors. Although diet has been identified as one of the major environmental risk factors, the role of nutrients in the clinical management of CD patients has not yet been fully investigated. In this prospective observational study, fifty-four patients diagnosed with active Crohn's disease and undergoing anti-TNF-α biological therapy were enrolled and subjected to nutrient intake analysis through a daily food diary. Their nutrient intake and blood values were analyzed before and after 6 months of biological therapy. After 6 months of anti-TNF-α, four patients dropped out of the study, leaving 29 patients in clinical remission and 21 still with active disease that remained the same. The aim of this study was to identify nutrients whose intake or blood values may be associated with patients' responses to biological therapy. In the diet, patients remaining with active CD showed very similar nutrient dietary intake compared to patients achieving remission except for a trend for lower starting zinc intake, below the reference value. In the blood, instead, patients who did not respond to biological therapy showed significantly lower plasma values of iron and taurine before starting biological anti-TNF-α treatment.

Older Adults With Inflammatory Bowel Disease Are at Higher Risk of Developing Antibodies to Infliximab

Although older age is thought to confer immunosenescence, we found that older adults with inflammatory bowel disease are independently at higher risk to develop antibodies to infliximab. Additionally, older adults are less likely to receive escalated doses of infliximab.

Real-world impact of infliximab precision-guided dosing on management of patients with IBD

OBJECTIVES

Evaluate the clinical utility of a precision-guided dosing test for infliximab (IFX) and its impact on treatment decision-making for inflammatory bowel disease (IBD).

STUDY DESIGN

Prospective, multisite, clinical experience program.

METHODS

Health care providers were given access to PredictrPK IFX, a precision-guided dosing test, for their patients with IBD on maintenance IFX therapy. Blood samples were drawn 20 to 56 days post infusion. A Bayesian data assimilation tool used clinical and serologic data to generate individual pharmacokinetic profiles and forecast trough IFX. Results were reported to providers to aid in-therapy management decisions and the decision-making process was assessed through questionnaires. Relationships between forecasted IFX concentration, disease activity, and therapy management decisions were analyzed by logistic regression.

RESULTS

PredictrPK IFX was used for 275 patients with IBD by 37 providers. In 58% of cases, providers modified treatment plans based on the results, including dose modifications (41%; of these, one-third decreased dose) and discontinuation (8%) of IFX. Of the 42% where treatment was not modified, 97.5% had IFX levels of 5 µg/mL or greater. Patients with IFX concentrations less than 5 µg/mL were 3 and 7.3 times more likely to have active disease or discontinue IFX, respectively. There was unanimous agreement among providers who completed a postprogram survey that PredictrPK IFX was beneficial in guiding treatment decisions and added more value to their practice than routine therapeutic drug monitoring.

CONCLUSIONS

PredictrPK IFX enables earlier and more precise dose optimization of IFX in patients with IBD, exerting a substantial impact on treatment decisions that may result in improved health outcomes and overall cost savings.

The Combination of Predictive Factors of Pharmacokinetic Origin Associates with Enhanced Disease Control during Treatment of Pediatric Crohn's Disease with Infliximab

Infliximab (IFX) concentrations are a predictive factor (PF) of pharmacokinetic (PK) origin in the treatment of Crohn's disease (CD). We evaluated Clearance, another PF of PK origin, either alone or in combination with concentrations. They were evaluated from two cohorts, the first designed to receive standard dosing (n = 37), and the second designed to proactively target therapeutic IFX concentrations (n = 108). Concentrations were measured using homogeneous mobility shift assay. Clearance was estimated using the nonlinear mixed effects methods with Bayesian priors. C-reactive protein-based clinical remission (<3 mg/L in the absence of symptoms) was used for the disease control outcome measure. Longitudinal changes in disease control due to factors including time, IFX concentration, and Clearance were analyzed using repeated event analysis. Change in objective function value (∆OFV) was calculated to compare concentration and Clearance. The results indicated that lower baseline Clearance and proactive dosing associated with enhanced disease control during induction (p < 0.01). Higher IFX concentrations and lower Clearance measured at the second, third, and fourth infusion yielded improved disease control during maintenance (p < 0.032). During maintenance, the association with disease control was better with Clearance than with concentrations (∆OFV = -19.2; p < 0.001), and the combination of both further minimized OFV (p < 0.001) with markedly improved clinical yield in the presence of both PF of PK origin. We conclude that the combination of IFX concentration and Clearance are better predictors of therapeutic outcome compared with either one alone.

Correlations Between Gastrointestinal Symptoms and Endoscopic-Histologic Disease Activity in Adults with Ulcerative Colitis

INTRODUCTION

Discordance between gastrointestinal (GI) symptoms and endoscopic inflammation in patients with ulcerative colitis (UC) is known. However, the correlations between symptoms and endoscopic and histologic (endo-histologic) mucosal healing and remains unknown.

METHODS

We performed a secondary analysis of prospectively collected clinical, endoscopic, and histologic data on 254 colonoscopies from 179 unique adults at a tertiary referral center from 2014 to 2021. Spearman's rank was used to assess the correlation between patient reported outcomes and objective assessments of disease activity, as measured by validated instruments: Two-item patient-reported outcome measure (PRO-2) for stool frequency and rectal bleeding, the Ulcerative Colitis Endoscopic Index of Severity (UCEIS) for endoscopic inflammation, and the Geboes score for histologic inflammation. The predictive value of objective assessments of inflammation and clinical symptoms was described using sensitivity, specificity, and positive/negative predictive value.

RESULTS

One-quarter (28%, 72/254) of cases were in endo-histologic remission; of these, 25% (18/72) report GI symptoms (22% diarrhea; 6% rectal bleeding). Endo-histologically active disease had higher sensitivity (95% rectal bleeding; 87% diarrhea) and negative predictive value (94% rectal bleeding, 78% diarrhea) for clinically active disease compared to active disease on endoscopic (77%) or histologic assessment only (80%). The specificity of endo/histologic inflammation for GI symptoms was < 65%. PRO-2 was positively correlated with endoscopic disease activity (Spearman's rank 0.57, 95% CI 0.54-0.60, p < 0.0001) and histologic disease activity (Spearman's rank 0.49, 0.45-0.53, p < 0.0001).

CONCLUSION

One-quarter of patients with ulcerative colitis in endo-histologic (deep) remission have gastrointestinal symptoms, more commonly with diarrhea than rectal bleeding. Endo-histologic inflammation has high sensitivity (≥ 87%) for diarrhea/rectal bleeding.

Anti-Integrin αvβ6 Autoantibodies Are a Novel Biomarker That Antedate Ulcerative Colitis

BACKGROUND & AIMS

Better biomarkers for prediction of ulcerative colitis (UC) development and prognostication are needed. Anti-integrin αvβ6 (anti-αvβ6) autoantibodies have been described in patients with UC. We tested for the presence of anti-αvβ6 antibodies in the preclinical phase of UC and studied their association with disease-related outcomes after diagnosis.

METHODS

Anti-αvβ6 autoantibodies were measured in 4 longitudinal serum samples collected from 82 subjects who later developed UC and 82 matched controls from a Department of Defense preclinical cohort (PREDICTS [Proteomic Evaluation and Discovery in an IBD Cohort of Tri-service Subjects]). In a distinct, external validation cohort (Crohn's and Colitis Canada Genetic Environmental Microbial project cohort), we tested 12 pre-UC subjects and 49 matched controls. Furthermore, anti-αvβ6 autoantibodies were measured in 2 incident UC cohorts (COMPASS [Comprehensive Care for the Recently Diagnosed IBD Patients], n = 55 and OSCCAR [Ocean State Crohn's and Colitis Area Registry], n = 104) and associations between anti-αvβ6 autoantibodies and UC-related outcomes were defined using Cox proportional hazards model.

RESULTS

Anti-αvβ6 autoantibodies were significantly higher among individuals who developed UC compared with controls up to 10 years before diagnosis in PREDICTS. The anti-αvβ6 autoantibody seropositivity was 12.2% 10 years before diagnosis and increased to 52.4% at the time of diagnosis in subjects who developed UC compared with 2.7% in controls across the 4 time points. Anti-αvβ6 autoantibodies predicted UC development with an area under the curve of at least 0.8 up to 10 years before diagnosis. The presence of anti-αvβ6 autoantibodies in preclinical UC samples was validated in the GEM cohort. Finally, high anti-αvβ6 autoantibodies was associated with a composite of adverse UC outcomes, including hospitalization, disease extension, colectomy, systemic steroid use, and/or escalation to biologic therapy in recently diagnosed UC.

CONCLUSIONS

Anti-integrin αvβ6 autoantibodies precede the clinical diagnosis of UC by up to 10 years and are associated with adverse UC-related outcomes.

Dietary Habits and Nutrient Deficiencies in a Cohort of European Crohn's Disease Adult Patients

Wrong dietary habits, such as the Western-style diet, are considered important risk factors for the development of Inflammatory Bowel Diseases (IBDs). Nevertheless, the role of dietary patterns in the clinical management of IBD patients has not been fully investigated yet. Fifty-four patients diagnosed with active Crohn's disease (CD) were enrolled and subjected to nutritional intake analysis through a weekly food diary. Nutritional patterns were analyzed, and nutrient intake was compared with those of 30 healthy subjects (HS). Blood levels of cholesterol, folic acid, minerals (K, Mg, Fe) and amino acids, were measured in CD patients to assess the presence of nutritional deficiencies. CD patients, with respect to HS, consumed significantly lower amounts of fiber, vitamins (A, E, C, B6, folic acid) and β-carotene. Their calcium, potassium, phosphorus, iron, magnesium, copper and iodine intake were also found to be significantly lower. In blood, CD patients had significantly lower concentrations of total cholesterol, potassium, iron, and amino acids. Active CD patient diet was significantly different from those of HS and may contribute to the establishment of nutritional deficiencies. Intestinal malabsorption was evidenced in these patients. Correction of the diet with specific nutritional plans is a necessary therapeutic step for these patients. ClinicalTrials.gov: NCT02580864.

Erythrocyte complement receptor 1 (ECR1) and erythrocyte-bound C4d (EC4d) in the prediction of poor pregnancy outcomes in systemic lupus erythematosus (SLE)

BACKGROUND

Complement activation has been associated with adverse pregnancy outcomes (APO) in SLE. Pregnant women with SLE were studied to evaluate whether complement dysregulation within the first two pregnancy trimesters predicts APO.

METHODS

Pregnant women fulfilled classification criteria for SLE. APO included neonatal death, preterm delivery before 36 weeks and small for gestational age newborn. Pre-eclampsia was also evaluated. Erythrocyte complement receptor 1 (ECR1) and erythrocyte-bound C4d (EC4d) were measured by flow cytometry. Complement proteins C3 and C4 were measured by immunoturbidimetry and anti-double-stranded DNA by ELISA in serum. Statistical analysis consisted of t-test, confusion matrix-derived diagnostic analysis, and multivariate logistic regression.

RESULTS

Fifty-one women had 57 pregnancies and 169 visits during the study. Baseline visits occurred mainly in the first (n=32) and second trimester (n=21). Fourteen (24.6%) pregnancies resulted in 21 APO with preterm delivery being the most common (n=10). ECR1 <5.5 net mean fluorescence intensity in the first trimester predicted APO with a diagnostic OR (DOR) of 18.33 (95% CI: 2.39 to 140.4; t-test p=0.04). Other individual biomarkers did not reach statistical significance. To estimate the likelihood of APO, we developed an algorithm that included the week of pregnancy, ECR1 and EC4d. From this algorithm, a Pregnancy Adversity Index (PAI) was calculated, and a PAI >0 indicated an elevated likelihood of pregnancy complications (DOR: 20.0 (95% CI: 3.64 to 109.97)).

CONCLUSIONS

Low levels of ECR1 in early or mid-pregnancy are predictive of an APO. Incorporating the weeks of gestation and both ECR1 and EC4d generated a PAI, which further predicted serious pregnancy complications.

Non-invasive Serological Monitoring for Crohn's Disease Postoperative Recurrence

INTRODUCTION

Crohn's disease recurs after intestinal resection. This study evaluated accuracy of a new blood test, the Endoscopic Healing Index [EHI], in monitoring for disease recurrence.

METHODS

Patients enrolled in the prospective POCER study [NCT00989560] underwent a postoperative colonoscopic assessment at 6 [2/3 of patients] and 18 months [all patients] following bowel resection, using the Rutgeerts score [recurrence ≥i2]. Serum was assessed at multiple time points for markers of endoscopic healing using the EHI, and paired with the Rutgeerts endoscopic score as the reference standard.

RESULTS

A total of 131 patients provided 437 serum samples, which were paired with endoscopic assessments available in 94 patients [30 with recurrence] at 6 months and 107 patients [44 with recurrence] at 18 months. The median EHI at 6 months was significantly lower in patients in remission [Rutgeerts <i2] than those with recurrence; p = 0.033. The area under the receiver operating curve [AUROC] for EHI to detect recurrence at 6 months was comparable to that of faecal calprotectin [0.712 vs 0.779, p = 0.414]. EHI of <20 at 6 months had a negative predictive value of 75.7% (95% confidence interval [CI] 58.8-88.2), and sensitivity of 70% [95% CI 50.6-85.3] for detecting recurrence. Combining all time points, an EHI <20 had a negative predictive value of 70.3%. Changes in EHI significantly associated with changes in Rutgeerts scores over the 18 months.

CONCLUSIONS

The non-invasive multi-marker EHI has sufficient accuracy to be used to monitor for postoperative Crohn's disease recurrence. A monitoring strategy that combines EHI with ileocolonoscopy, with or without faecal calprotectin, should now be prospectively tested.

Model Informed Precision Dosing Tool Forecasts Trough Infliximab and Associates with Disease Status and Tumor Necrosis Factor-Alpha Levels of Inflammatory Bowel Diseases

Background: Substantial inter-and intra-individual variability of Infliximab (IFX) pharmacokinetics necessitates tailored dosing approaches. Here, we evaluated the performances of a Model Informed Precision Dosing (MIPD) Tool in forecasting trough Infliximab (IFX) levels in association with disease status and circulating TNF-α in patients with Inflammatory Bowel Diseases (IBD). Methods: Consented patients undergoing every 8-week maintenance therapy with IFX were enrolled. Midcycle specimens were collected, IFX, antibodies to IFX, albumin were determined and analyzed with weight using nonlinear mixed effect models coupled with Bayesian data assimilation to forecast trough levels. Accuracy of forecasted as compared to observed trough IFX levels were evaluated using Demings’s regression. Association between IFX levels, CRP-based clinical remission and TNF-α levels were analyzed using logistic regression and linear mixed effect models. Results: In 41 patients receiving IFX (median dose = 5.3 mg/Kg), median IFX levels decreased from 13.0 to 3.9 µg/mL from mid to end of cycle time points, respectively. Midcycle IFX levels forecasted trough with Deming’s slope = 0.90 and R2 = 0.87. Observed end cycle and forecasted trough levels above 5 µg/mL associated with CRP-based clinical remission (OR = 7.2 CI95%: 1.7−30.2; OR = 21.0 CI95%: 3.4−127.9, respectively) (p < 0.01). Median TNF-α levels increased from 4.6 to 8.0 pg/mL from mid to end of cycle time points, respectively (p < 0.01). CRP and TNF-α levels associated independently and additively to decreased IFX levels (p < 0.01). Conclusions: These data establish the value of our MIPD tool in forecasting trough IFX levels in patients with IBD. Serum TNF-α and CRP are reflective of inflammatory burden which impacts exposure.

Performance Characteristics of a Clinical Decision Support Tool for Disease Complications in Crohn's Disease

Background

Patients with Crohn's disease (CD) are at risk of complications. Performance characteristics of a decision support tool assessing the risk of CD complications were evaluated.

Methods

CDPATH (formerly called the Personalized Risk and Outcome Prediction Tool [PROSPECT]) was calibrated and validated in 2 cohorts. Tool prediction of disease characteristics was assessed using Cox regression and Harrell's C-statistic.

Results

All associations of CD complications and CDPATH components were significant except perianal location. There was a significant association between individualized risk assessment scores and CD complications in both cohorts.

Conclusion

CDPATH is validated as a clinical decision support tool for assessing the risk of CD complications.

Platelet bound complement split product (PC4d) is a marker of platelet activation and arterial vascular events in Systemic Lupus Erythematosus

Platelet-bound complement activation products (PC4d) are associated with thrombosis in Systemic Lupus Erythematosus (SLE). This study investigated the effect of PC4d on platelet function, as a mechanistic link to arterial thrombosis. In a cohort of 150 SLE patients, 13 events had occurred within five years of enrollment. Patients with arterial events had higher PC4d levels (13.6 [4.4-24.0] vs. 4.0 [2.5-8.3] net MFI), with PC4d 10 being the optimal cutoff for event detection. The association of arterial events with PC4d remained significant after adjusting for antiphospholipid status, smoking, and prednisone use (p = 0.045). PC4d levels correlated with lower platelet counts (r = -0.26, p = 0.002), larger platelet volumes (r = 0.22, p = 0.009) and increased platelet aggregation: the adenosine diphosphate (ADP) concentration to achieve 50% maximal aggregation (EC₅₀) was lower in patients with PC4d 10 compared with PC4d < 10 (1.6 vs. 3.7, p = 0.038, respectively). These results suggest that PC4d may be a mechanistic marker for vascular disease in SLE.

Cell-bound complement activation products associate with lupus severity in SLE

Objectives

To evaluate the association between lupus severity and cell-bound complement activation products (CB-CAPs) or low complement proteins C3 and C4.

Methods

All subjects (n=495) fulfilled the American College of Rheumatology (ACR) classification criteria for SLE. Abnormal CB-CAPs (erythrocyte-bound C4d or B-lymphocyte-bound C4d levels >99th percentile of healthy) and complement proteins C3 and C4 were determined using flow cytometry and turbidimetry, respectively. Lupus severity was estimated using the Lupus Severity Index (LSI). Statistical analysis consisted of multivariable linear regression and groups comparisons.

Results

Abnormal CB-CAPs were more prevalent than low complement values irrespective of LSI levels (62% vs 38%, respectively, p<0.0001). LSI was low (median 5.44, IQR: 4.77–6.93) in patients with no complement abnormality, intermediate in patients with abnormal CB-CAPs (median 6.09, IQR: 5.31–8.20) and high in the group presenting with both abnormal CB-CAPs and low C3 and/or C4 (median 7.85, IQR: 5.51–8.37). Odds of immunosuppressant use was higher in subjects with LSI ≥5.95 compared with subjects with LSI <5.95 (1.60 vs 0.53, p<0.0001 for both). Multivariable regression analysis revealed that higher LSI scores associated with abnormal CB-CAPs—but not low C3/C4—after adjusting for younger age, race and longer disease duration (p=0.0001), which were also independent predictors of disease severity (global R²=0.145).

Conclusion

Abnormalities in complement activation as measured by CB-CAPs are associated with increased LSI.

Use of the Endoscopic Healing Index for Monitoring of Disease Activity in Patients With Crohn's Disease in the COVID Era

Management of Crohn’s disease (CD) during COVID-19 is challenging when colonoscopy is not feasible. This study describes a blood-based test that has been validated against colonoscopy in patients with CD as an alternative even in patients with high inflammation from infections.

Complement Activation in Patients With Probable Systemic Lupus Erythematosus and Ability to Predict Progression to American College of Rheumatology-Classified Systemic Lupus Erythematosus

Objective

To evaluate the frequency of cell‐bound complement activation products (CB‐CAPs) as a marker of complement activation in patients with suspected systemic lupus erythematosus (SLE) and the usefulness of this biomarker as a predictor of the evolution of probable SLE into SLE as classified by the American College of Rheumatology (ACR) criteria.

Methods

Patients in whom SLE was suspected by lupus experts and who fulfilled 3 ACR classification criteria for SLE (probable SLE) were enrolled, along with patients with established SLE as classified by both the ACR and the Systemic Lupus International Collaborating Clinics (SLICC) criteria, patients with primary Sjögren's syndrome (SS), and patients with other rheumatic diseases. Individual CB‐CAPs were measured by flow cytometry, and positivity rates were compared to those of commonly assessed biomarkers, including serum complement proteins (C3 and C4) and autoantibodies. The frequency of a positive multianalyte assay panel (MAP), which includes CB‐CAPs, was also evaluated. Probable SLE cases were followed up prospectively.

Results

The 92 patients with probable SLE were diagnosed more recently than the 53 patients with established SLE, and their use of antirheumatic medications was lower. At the enrollment visit, more patients with probable SLE were positive for CB‐CAPs (28%) or MAP (40%) than had low complement levels (9%) (P = 0.0001 for each). In probable SLE, MAP scores of >0.8 at enrollment predicted fulfillment of a fourth ACR criterion within 18 months (hazard ratio 3.11, P < 0.01).

Conclusion

Complement activation occurs in some patients with probable SLE and can be detected with higher frequency by evaluating CB‐CAPs and MAP than by assessing traditional serum complement protein levels. A MAP score above 0.8 predicts transition to classifiable SLE according to ACR criteria.

Transition of Methotrexate Polyglutamate Drug Monitoring Assay from Venipuncture to Capillary Blood-Based Collection Method in Rheumatic Diseases

Objective

Methotrexate (MTX) polyglutamate (MTXPG3) levels from isolated red blood cells (RBCs) collected by venipuncture have clinical utility in guiding MTX dosing for patients with rheumatoid arthritis (RA). Our objective was to transition this RBC-based therapeutic drug monitoring (TDM) assay to dried capillary blood collected by fingerstick.

Methods

Patients with RA treated with MTX were enrolled. Specimens were collected by fingerstick (volumetric absorptive microsampler) and venipuncture to measure MTXPG3 from dried capillary blood, total venous blood, and isolated RBCs. MTXPG3 levels from dried capillary blood were measured using LC-MS/MS, converted to RBC equivalent (nmol/L), and compared with those from isolated RBCs (reference method). Following transition to fingerstick collection, comparability in the distributions of dried capillary and venipuncture-based RBC MTXPG3 levels was assessed using the Kolmogorov–Smirnov (K-S) test.

Results

Intraday and interday precision ranged from 2.0% to 10.9% and 3.1% to 10.8%, respectively, at MTXPG3 concentrations ranging from 5 to 100 nmol/L. In 106 participants treated with MTX, MTXPG3 levels from total venous and dried capillary blood were comparable [slope = 0.97 (95% CI, 0.92–1.03); R2 = 0.92]. Dried capillary blood MTXPG3 converted to RBC equivalent was similar to levels from isolated RBCs (30 ± 18 nmol/L vs 33 ± 19 nmol/L; n = 106). After implementation in the clinical laboratory, RBC equivalents MTXPG3 from the fingerstick method were similar to levels from venipuncture [39 ± 22 nmol/L (n = 825) vs 39 ± 24 nmol/L (n = 47935)] (K-S test P = 0.09). Underexposure to MTX (MTXPG3 ≤5 nmol/L RBCs) was detected in 7.0% and 8.5% patient specimens collected using the fingerstick and venipuncture methods, respectively.

Conclusion

Capillary blood MTXPG3 levels can be used to guide MTX dosing in TDM practice.

Randomised prospective trial to assess the clinical utility of multianalyte assay panel with complement activation products for the diagnosis of SLE

Objective

We compared the physician-assessed diagnostic likelihood of SLE resulting from standard diagnosis laboratory testing (SDLT) to that resulting from multianalyte assay panel (MAP) with cell-bound complement activation products (MAP/CB-CAPs), which reports a two-tiered index test result having 80% sensitivity and 86% specificity for SLE.

Methods

Patients (n=145) with a history of positive antinuclear antibody status were evaluated clinically by rheumatologists and randomised to SDLT arm (tests ordered at the discretion of the rheumatologists) or to MAP/CB-CAPs testing arm. The primary endpoint was based on the change in the physician likelihood of SLE on a five-point Likert scale collected before and after testing. Changes in pharmacological treatment based on laboratory results were assessed in both arms. Statistical analysis consisted of Wilcoxon and Fisher’s exact tests.

Results

At enrolment, patients randomised to SDLT (n=73, age=48±2 years, 94% females) and MAP/CB-CAPs testing arms (n=72, 50±2 years, 93% females) presented with similar pretest likelihood of SLE (1.42±0.06 vs 1.46±0.06 points, respectively; p=0.68). Post-test likelihood of SLE resulting from randomisation in the MAP/CB-CAPs testing arm was significantly lower than that resulting from randomisation to SDLT arm on review of test results (−0.44±0.10 points vs −0.19±0.07 points) and at the 12-week follow-up visit (−0.61±0.10 points vs −0.31±0.10 points) (p<0.05). Among patients randomised to the MAP/CB-CAPs testing arm, two-tiered positive test results associated significantly with initiation of prednisone (p=0.034).

Conclusion

Our data suggest that MAP/CB-CAPs testing has clinical utility in facilitating SLE diagnosis and treatment decisions.

Association between hydroxychloroquine levels and disease activity in a predominantly Hispanic systemic lupus erythematosus cohort

OBJECTIVES

Hydroxychloroquine (HCQ) is a key therapy in systemic lupus erythematosus (SLE). Medication non-adherence is reported in up to 80% of lupus patients and results in increased morbidity, mortality, and health care utilization. HCQ levels are a sensitive and reliable method to assess medication adherence. Our study evaluated the role of HCQ level measurement in routine clinical care and its association with disease activity in a predominantly Hispanic population.

METHODS

SLE patients from the Columbia University Lupus cohort treated with HCQ for ≥ 6 months and reporting medication adherence were included. HCQ levels were measured by whole blood high performance liquid chromatography. Non-adherence was defined as an HCQ level <500 ng/ml. The association between HCQ levels and disease activity measured by Systemic Lupus Erythematosus Disease Activity Index 2000 (SLEDAI-2K) was evaluated.

RESULTS

One hundred and eight patients were enrolled; the median age was 38 years, 91% were female, and 63% were Hispanic. The median SLEDAI-2K was 4.3 (0-20). Forty-one percent of patients had an HCQ level <500 ng/ml consistent with non-adherence, of which 19% had undetectable levels. A higher SLEDAI-2K score was associated with low HCQ levels (p = 0.003). This association remained significant after adjusting for depression (p = 0.0007).

CONCLUSION

HCQ levels < 500 ng/ml were associated with higher disease activity and accounted for 32% of the SLEDAI-2K variability. HCQ blood measurement is a simple and reliable method to evaluate medication adherence in SLE. Reasons for non-adherence (levels < 500 ng/ml) should be further explored and addressed.

Cell bound complement activation products alone and in combination with low serum complement C3 or C4 have superior diagnostic performance in systemic lupus erythematosus

BACKGROUND

Cell-bound complement activation products (CB-CAPs) are sensitive and specific diagnostic markers of systemic lupus erythematosus (SLE). We compared the performance of CB-CAPs to low serum complement C3 or C4 in distinguishing SLE from other rheumatic diseases and healthy individuals.

METHODS

Adult subjects (n=1200) were enrolled from multiple academic centers, including SLE (498), healthy individuals (252) and subjects with other rheumatic diseases (450). Erythrocyte bound C4d [EC4d] and B-Lymphocyte bound C4d [BC4d] were quantitated using flow cytometry. Serum C3 and C4 levels were determined using immunoturbidimetry. Measurements included sensitivity, specificity, area under the curve (AUC) of the receiver operating characteristic curve (ROC) and Youden Index, for each marker as well as combinations.

RESULTS

Abnormal CB-CAPs status yielded 62% sensitivity with 88% specificity in distinguishing SLE from the group with other diseases compared to low C3/C4 status − 38% sensitivity, 93% specificity. Youden index was 0.492±0.03 for CB-CAPs compared to 0.313±0.03 for low C3/C4 (p&lt;0.01). AUC was higher with BC4d (0.72) than with EC4d (0.68; p&lt;0.01), low C3 (0.62; p&lt;0.01), low C4 (0.62; p&lt;0.01) and low C3 and/or C4 levels (0.66; p&lt;0.01).

The cumulative complement scoring system yielded higher AUC (0.81). A score with greater than 1 complement abnormality yielded 45% sensitivity and 98% specificity.

CONCLUSION

Our data suggests that CB-CAPs have greater diagnostic performance than low serum complement C3/C4. The combination of these complement abnormalities in a composite complement score is superior in distinguishing SLE from other rheumatic diseases and healthy individuals.

Platelet-bound C4d, low C3 and lupus anticoagulant associate with thrombosis in SLE

Background

Low C3 and lupus anticoagulant (LAC) are known risk factors for thrombosis in SLE. We evaluated the association between C4d products deposited on platelets (PC4d) and thrombosis in SLE. Antiphosphatidyl serine/prothrombin (PS/PT) complex antibody was also evaluated as an alternative to LAC.

Methods

This was a cross-sectional analysis of 149 consented patients with SLE (mean age: 47±1 years, 86% female) classified with (n=16) or without (n=133) thrombotic events in the past 5 years. Abnormal PC4d (≥20 units) was measured using flow cytometry. LAC and C3 were measured using dilute Russell’s viper venom time (>37 s) and immunoturbidimetry, respectively. Anti-PS/PT antibody status (IgG) was measured by immunoassay. Statistical analysis consisted of logistic regression and calculation of OR estimates with 95% CI.

Results

Abnormal PC4d (OR=8.4, 95% CI 2.8 to 24.8), low C3 (OR=9.5, 95% CI 3.0 to 30.3), LAC (OR=5.4, 95% CI 1.3 to 22.3) and anti-PS/PT IgG (OR=3.4, 95% CI 1.2 to 9.7) status associated with thrombosis (p<0.05). Cumulatively, the presence of PC4d, low C3 and LAC abnormalities as a composite risk score was higher in the presence of thrombosis (1.93±0.25) than in its absence (0.81±0.06) (p<0.01). Each unit of this composite risk score yielded an OR of 5.2 (95% CI 2.5 to 10.7) to have thrombosis (p<0.01). The composite risk score with anti-PS/PT antibody status instead of LAC also associated with thrombosis (p<0.01).

Conclusion

A composite risk score including PC4d, low C3 and LAC was associated with recent thrombosis and acknowledges the multifactorial nature of thrombosis in SLE.

Cell-bound complement activation products (CB-CAPs) have high sensitivity and specificity in pediatric-onset systemic lupus erythematosus and correlate with disease activity

OBJECTIVE

Elevated levels of cell-bound complement activation products (CB-CAPs) (C4d deposition on B lymphocytes (BC4d) and/or erythrocytes (EC4d)) are sensitive and specific in diagnosis and monitoring of adult systemic lupus erythematosus (SLE). Our objective was to evaluate the role of CB-CAPs for diagnosis and monitoring of pediatric-onset SLE (pSLE).

METHODS

A prospective cohort study of 28 pSLE and 22 juvenile arthritis patients was conducted. SLE disease activity was determined using a clinical Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) that excluded serologies. Autoantibodies were measured using solid-phase immunoassays, C3 and C4 using immunoturbidimetry, and CB-CAPs using quantitative flow cytometry. Abnormal CB-CAPs were defined as EC4d or BC4d above the 99th percentile for healthy adults (>14 and > 60 net mean fluorescence intensity (MFI), respectively). Performance characteristics of CB-CAPs were assessed using area under the curve (AUC) for receiver operating characteristics. Linear mixed effect models evaluated the correlation between CB-CAPs and clinical SLEDAI over 6 months.

RESULTS

BC4d yielded higher AUC (0.91 ± 0.04) than C3 (0.63 ± 0.08) and C4 (0.67 ± 0.08) ( p < 0.05). Abnormal CB-CAPs were 78% sensitive and 86% specific for diagnosis of pSLE (Youden's index = 0.64 ± 0.11). In contrast to BC4d, EC4d levels correlated with clinical SLEDAI ( p < 0.01).

CONCLUSION

CB-CAPs (EC4d and BC4d) have higher sensitivity and specificity than low complement in pSLE, and may help with diagnosis of pSLE. EC4d could provide a useful biomarker for disease activity monitoring.

Erythrocyte-bound C4d in combination with complement and autoantibody status for the monitoring of SLE

Background

We examined the usefulness of erythrocyte-bound C4d (EC4d) to monitor disease activity in SLE.

Methods

Data and blood samples were collected from three different studies, each of which included longitudinal evaluations using the Physicians Global Assessment (PGA) of disease activity and the Safety of Estrogens in Lupus Erythematosus National Assessment (SELENA) SLE Disease Activity Index (SLEDAI), which was assessed without anti-double-stranded DNA (dsDNA) and low complement C3/C4 (clinical SELENA-SLEDAI). EC4d levels were determined using flow cytometry; other laboratory measures included antibodies to dsDNA, C3 and C4 proteins. Relationships between clinical SELENA-SLEDAI, PGA and the laboratory measures were analysed using linear mixed effect models.

Results

The three studies combined enrolled 124 patients with SLE (mean age 42 years, 97% women, 31% Caucasians and 34% African-Americans) followed for an average of 5 consecutive visits (range 2-13 visits). EC4d levels and low C3/C4 status were significantly associated the clinical SELENA-SLEDAI or PGA in each of the three study groups (p<0.05). Multivariate analysis revealed that EC4d levels (estimate=0.94±0.28) and low complement C3/C4 (estimate=1.24±0.43) were both independently and significantly associated with the clinical SELENA-SLEDAI (p<0.01) and PGA. EC4d levels were also associated with the clinical SELENA-SLEDAI (estimate: 1.20±0.29) and PGA (estimate=0.19±0.04) among patients with chronically low or normal C3/C4 (p<0.01). Anti-dsDNA titres were generally associated with disease activity.

Conclusion

These data support the association of EC4d with disease activity regardless of complement C3/C4 status and its usefulness in monitoring SLE disease. Additional studies will be required to support these validation data.

Cell-bound complement activation products in SLE

Diagnosis of SLE is based on clinical manifestations and laboratory findings. Timely diagnosis and treatment are important to control disease activity and prevent organ damage. However, diagnosis is challenging because of the heterogeneity in clinical signs and symptoms, and also because the disease presents with alternating periods of flare and quiescence. As SLE is an autoimmune disease characterised by the formation of autoantibodies, diagnostic immunology laboratory tests for detecting and quantifying autoantibodies are commonly used for the diagnosis and classification of SLE. These include ANA, anti-double-stranded DNA antibodies and anti-Smith antibodies, together with other antibodies such as antiphospholipid or anti-Cq1. Complement proteins C3 and C4 are commonly measured in patients with SLE, but their serum levels do not necessarily reflect complement activation. Cell-bound complement activation products (CB-CAPs) are fragments formed upon complement activation that bind covalently to haematopoietic cells. This review focuses on the complement system and, in particular, on CB-CAPs as biomarkers for the diagnosis and monitoring of SLE, vis-à-vis complement proteins and other biomarkers of complement activation.

Validation of a multi-analyte panel with cell-bound complement activation products for systemic lupus erythematosus

BACKGROUND

We describe the analytical validation of an assay panel intended to assist clinicians with the diagnosis of systemic lupus erythematosus (SLE). The multi-analyte panel includes quantitative assessment of complement activation and measurement of autoantibodies.

METHODS

The levels of the complement split product C4d bound to erythrocytes (EC4d) and B-lymphocytes (BC4d) (expressed as mean fluorescence intensity [MFI]) are measured by quantitative flow cytometry, while autoantibodies (inclusive of antinuclear and anti-double stranded DNA antibodies) are determined by immunoassays. Results of the multi-analyte panel are reported as positive or negative based on a 2-tiered index score. Post-phlebotomy stability of EC4d and BC4d in EDTA-anticoagulated blood is determined using specimens collected from patients with SLE and normal donors. Three-level C4 coated positive beads are run daily as controls. Analytical validity is reported using intra-day and inter-day coefficient of variation (CV).

RESULTS

EC4d and BC4d are stable for 2days at ambient temperature and for 4days at 4°C post-phlebotomy. Median intra-day and inter-day CV range from 2.9% to 7.8% (n=30) and 7.3% to 12.4% (n=66), respectively. The 2-tiered index score is reproducible over 4 consecutive daysupon storage of blood at 4°C. A total of 2,888 three-level quality control data were collected from 6 flow cytometers with an overall failure rate below 3%. Median EC4d level is 6 net MFI (Interquartile [IQ] range 4-9 net MFI) and median BC4d is 18 net MFI (IQ range 13-27 net MFI) among 86,852 specimens submitted for testing. The incidence of 2-tiered positive test results is 13.4%.

CONCLUSION

We have established the analytical validity of a multi-analyte assay panel for SLE.

Capillary blood collected on volumetric absorptive microsampling (VAMS) device for monitoring hydroxychloroquine in rheumatoid arthritis patients

A novel technique for collection of capillary blood, termed volumetric absorptive microsampling (VAMS), has been recently cleared by the FDA for collection of human blood. VAMS absorbs a fixed volume of blood (10μl) and overcomes area bias and homogeneity issues associated with dried blood spot (DBS). This study is the application of VAMS for therapeutic drug monitoring (TDM) in human capillary blood. A liquid chromatography-tandem mass spectrometry (LC-MS/MS) workflow for analysis of VAMS sample was developed and validated. Concentration of hydroxychloroquine (HCQ) and its metabolites, desethylhydroxychloroquine (DHCQ), desethylchloroquine (DCQ), and bisdesethylchloroquine (BDCQ), in capillary blood on VAMS sampler were compared to those in venous blood in rheumatoid arthritis patients. Feasibility of capillary blood collected on both VAMS and DBS card were evaluated on patients. Stability of dried capillary blood on VAMS was also examined. Our results established that VAMS is a simple and accurate sampling technique that delivers the benefits of DBS sampling while overcoming the issues associated with hematocrit and homogeneity. It requires a small blood volume, simplifies sample logistics management, and may allow sample collection in the patient's home setting.

Reduction in erythrocyte-bound complement activation products and titres of anti-C1q antibodies associate with clinical improvement in systemic lupus erythematosus

Background

The relationship between cell-bound complement activation products (CB-CAPs: EC4d, EC3d), anti-C1q, soluble complement C3/C4 and disease activity in systemic lupus erythematosus (SLE) was evaluated.

Methods

Per protocol, at baseline all SLE subjects enrolled in this longitudinal study presented with active disease and elevated CB-CAPs. At each monthly visit, the non-serological (ns) Safety of Estrogens in Lupus Erythematosus: National Assessment (SELENA-SLEDAI) and the British Isles Lupus Assessment Group (BILAG)-2004 index scores were determined as was a random urinary protein to creatinine ratio (uPCR). Short-form 36 (SF-36) questionnaires were also collected. All soluble markers were determined using immunoassays, while EC4d and EC3d were determined using flow cytometry. Statistical analysis consisted of linear mixed models with random intercept and fixed slopes.

Results

A total of 36 SLE subjects (mean age 34 years; 94% female) were enrolled and evaluated monthly for an average 11 visits per subject. Clinical improvements were observed during the study, with significant decreases in ns-SELENA-SLEDAI scores, BILAG-2004 index scores and uPCR, and increases in all domains of SF-36 (p<0.01). The longitudinal decrease in ns-SELENA-SLEDAI and BILAG-2004 index scores was significantly associated with reduced EC4d and EC3d levels, reduced anti-C1q titres and increased serum complement C3/C4 (p<0.05). The changes in uPCR significantly correlated with C3, C4, anti-C1q and EC4d, with EC4d outperforming C3/C4 by a multivariate analysis. The reduced EC4d or EC3d was associated with improvements in at least six out of the eight domains of SF-36 and outperformed C3/C4. Anti-dsDNA titres did not correlate with changes in disease activity.

Conclusions

These data indicate that CB-CAPs and anti-C1q are helpful in monitoring patients with SLE.

Detection of anti-dsDNA antibodies by computer-aided automated immunofluorescence analysis

INTRODUCTION

NOVA View is a computer aided fluorescence microscope that is used for the automated reading and interpretation of indirect immunofluorescent tests in diagnostic immunology. The objective of the present study was to evaluate the performance of the NOVA View® system for the measurement of anti-dsDNA antibodies using the Crithidia luciliae indirect immunofluorescence test (CLIFT) technology.

METHODS

Analytical performance of NOVA View CLIFT was assessed in repeatability (within run) and reproducibility (between runs and instruments) studies. Two hundred-fifty patient samples (N=200 consecutive samples and N=50 samples from systemic lupus erythematosus patients) were tested to evaluate the agreement between results generated with NOVA View CLIFT, and those obtained with manual microscopic reading of the same slides. Positivity rate in SLE was assessed on the 50 SLE samples.

RESULTS

The NOVA View system showed high level of repeatability and reproducibility within runs, between runs, and between instruments. Agreement of NOVA View software interpretation and digital image reading results with manual microscopic reading results was 96.0%, and the same positivity rate was obtained on SLE samples by NOVA View digital image reading as that of manual microscopic reading (36.0% vs. 38.0%, respectively).

CONCLUSION

Results generated by NOVA View CLIFT were equivalent to those obtained by manual microscopic reading on a large routine sample set. NOVA View demonstrated consistency within and between runs, and between instruments. Automation of CLIFT provides reliability and is a suitable alternative for routine clinical laboratories.

Systemic lupus erythematosus and primary fibromyalgia can be distinguished by testing for cell-bound complement activation products

OBJECTIVE

We sought to establish the performance of cell-bound complement activation products (CB-CAPs) as a diagnostic tool to distinguish primary fibromyalgia (FM) from systemic lupus erythematosus (SLE).

METHODS

A total of 75 SLE and 75 primary FM adult subjects who fulfilled appropriate classification criteria were enrolled prospectively. CB-CAPs (erythrocyte-C4d (EC4d) and B-lymphocyte-C4d (BC4d)) were determined by flow cytometry. Antinuclear antibodies (ANAs) were determined using indirect immunofluorescence while other autoantibodies were determined by solid-phase assays. The CB-CAPs in a multi-analyte assay with algorithm (MAAA) relied on two consecutive tiers of analysis that was reported as an overall positive or negative assessment. Test performance was assessed using sensitivity, specificity, positive and negative likelihood ratio (LR).

RESULTS

ANAs yielded 80% positives for SLE and 33% positives for FM. High CB-CAP expression (EC4d >14 units or BC4d >60 units) was 43% sensitive and 96% specific for SLE. The CB-CAPs in MAAA assessment was evaluable in 138 of the 150 subjects enrolled (92%) and yielded 60% sensitivity (CI 95% 48% to 72%) for SLE with no FM patient testing positive (100% specificity). A positive test result was associated with a strong positive LR for SLE (>24, CI 95%; 6 to 102), while a negative test result was associated with a moderate negative LR (0.40; CI 95% 0.30 to 0.54).

CONCLUSION

Our data indicate that CB-CAPs in MAAA can distinguish FM from SLE.

Cell-bound complement activation products in systemic lupus erythematosus: comparison with anti-double-stranded DNA and standard complement measurements

OBJECTIVE

To compare the performance characteristics of cell-bound complement (C4d) activation products (CBCAPS) on erythrocyte (EC4d) and B cells (BC4d) with antibodies to double-stranded DNA (anti-dsDNA) and complement C3 and C4 in systemic lupus erythematosus (SLE).

METHODS

The study enrolled 794 subjects consisting of 304 SLE and a control group consisting of 285 patients with other rheumatic diseases and 205 normal individuals. Anti-dsDNA and other autoantibodies were measured using solid-phase immunoassays while EC4d and BC4d were determined using flow cytometry. Complement proteins were determined using immunoturbidimetry. Disease activity in SLE was determined using a non-serological Systemic Lupus Erythematosus Disease Activity Index SELENA Modification. A two-tiered methodology combining CBCAPS with autoantibodies to cellular and citrullinated antigens was also developed. Statistical analyses used area under receiver operating characteristic curves and calculations of area under the curve (AUC), sensitivity and specificity.

RESULTS

AUC for EC4d (0.82±0.02) and BC4d (0.84±0.02) was higher than those yielded by C3 (0.73±0.02) and C4 (0.72±0.02) (p<0.01). AUC for CBCAPS was also higher than the AUC yielded by anti-dsDNA (0.79±0.02), but significance was only achieved for BC4d (p<0.01). The combination of EC4d and BC4d in multivariate testing methodology with anti-dsDNA and autoantibodies to cellular and citrullinated antigens yielded 80% sensitivity for SLE and specificity ranging from 70% (Sjogren's syndrome) to 92% (rheumatoid arthritis) (98% vs. normal). A higher proportion of patients with SLE with higher levels of disease activity tested positive for elevated CBCAPS, reduced complement and anti-dsDNA (p<0.03).

CONCLUSIONS

CBCAPS have higher sensitivity than standard complement and anti-dsDNA measurements, and may help with the differential diagnosis of SLE in combination with other autoantibodies.

Fibroblasts from methotrexate-sensitive mice accumulate methotrexate polyglutamates but those from methotrexate-resistant mice do not

OBJECTIVES

We and others have previously demonstrated that methotrexate (MTX) mediates its anti-inflammatory effects through an increase in cellular release of adenosine. Consistent with this observation, there is no increase in adenosine from exudates of mouse strains resistant to MTX. Because intracellular MTX polyglutamates inhibit AICAR transformylase (ATIC) activity and thereby promote adenosine release we determined whether there is any difference in the capacity of cells from MTX-resistant mice to accumulate MTX polyglutamates.

METHODS

Dermal fibroblasts (DF) from BALBc, MTX-sensitive, and DBA/1J, MTX-resistant, mice were cultured in the presence or absence of MTX. Adenosine concentration in the supernatant and intracellular MTX polyglutamate (MTXPG1-5) concentrations were measured by liquid chromatography. ATIC activity in DF was monitored spectrophotometrically by the formation of formytetrahydrofolate.

RESULTS

MTX (1 μM) increased adenosine production by DF from BALBc sensitive-mice from 269±40 nM to 446±4 nM. No adenosine production was found in supernates of cultured DF from DBA/1J mice regardless of MTX treatment. Intracellular MTX polyglutamates (MTXPG2-4) were detected only in BALBc DFs, not in DBA/1J DF. Further investigation demonstrated that ATIC activity was inhibited following MTX treatment in DF from BALBc mice.

CONCLUSIONS

These data suggest that resistance to the anti-inflammatory effects of MTX could be due to diminished MTX polyglutamate accumulation resulting in diminished ATIC inhibition and adenosine accumulation.

Patterns of interaction between genetic and nongenetic attributes and methotrexate efficacy in rheumatoid arthritis

OBJECTIVE

The contribution of low-penetrance single nucleotide polymorphisms to methotrexate efficacy in rheumatoid arthritis (RA) is inconsistent between studies. We sought to elucidate architecture of methotrexate response in three cohorts of patients with RA treated with methotrexate.

METHODS

Single nucleotide polymorphism frequencies in genes from folate, purine, and pyrimidine pathways were measured to develop a model of gene-gene interactions using multifactor dimensionality reduction in 439 patients who received methotrexate in the USA and The Netherlands. A third cohort of 530 patients with RA from Sweden was used to replicate the findings. Methotrexate efficacy was assessed using the European League Against Rheumatism criteria in the majority of patients.

RESULTS

Nonlinear patterns of gene-gene interactions between variants in aminoimidazole carboxamide ribonucleotide transformylase (C347G), reduced-folate carrier (G80A) and inosine-triphosphate pyrophosphatase (C94A) revealed a predisposing genetic attribute significantly associated with methotrexate response in the USA and Dutch cohorts [odds ratio (OR)=2.9, 95% confidence interval (CI): 1.9-4.2; P<0.001]. Although the finding was not replicated in the Swedish cohort (OR=0.9; 95% CI: 0.64-1.37; P=0.74) a multifactor dimensionality reduction analysis superimposing the predisposing genetic attribute with patient's age, sex, and anticitrullinated peptide antibodies positivity (ACPA) revealed a pattern of interaction significant in all three cohorts (OR=2.2, 95% CI: 1.6-2.9; P<0.01). The selective advantage toward response in the presence of the predisposing genetic attribute was lost in females and ACPA-positive patients, whereas older and male ACPA-negative patients tended to exhibit a greater likelihood of response in the absence of the predisposing genetic attribute.

CONCLUSION

Gene-gene interactions together with nongenetic attributes may contribute to methotrexate efficacy in RA.

Red blood cell methotrexate polyglutamates emerge as a function of dosage intensity and route of administration during pulse methotrexate therapy in rheumatoid arthritis

OBJECTIVE

MTX is a prodrug producing anti-arthritic effects through a folylpolyglutamate synthase-mediated activation to MTX polyglutamates (MTXPGs). Our objective was to characterize the pharmacokinetics of intracellular MTXPGs and the factors associated with their accumulation in adult RA patients treated with MTX weekly.

METHODS

MTX pharmacokinetics were evaluated in 47 MTX-naïve patients enrolled in an MTX dose-escalation study for an average of 20 weeks and 223 patients enrolled in a cross-sectional study under long-term MTX therapy. Short-chain (MTXPG1-2), long-chain (MTXPG3) and very long-chain (MTXPG4-5) concentrations were measured in circulating red blood cells using liquid chromatography. Statistical analyses consisted of non-linear mixed models, multivariate regression analyses and Wilcoxon signed-rank test.

RESULTS

The accumulation of MTXPG1-5 was sigmoidal and steady-state concentrations were achieved after 7 weeks of therapy. However, additional exposure and MTX dosage escalation produced a selective redistribution towards longer chain MTXPGs at the expense of shorter chain MTXPGs. Age, glomerular filtration rate and route of MTX administration were the most important predictors of MTXPG accumulation. In 10 patients, a switch from oral to parenteral MTX was associated with a 37% increase in long-chain MTXPGs, a 132% increase in very long-chain MTXPGs and a concomitant 31% reduction in disease activity (P<0.02).

CONCLUSION

The selective emergence of long-chain MTXPGs is function of dose, time of exposure and hence dosage intensity. Switching from oral to parenteral MTX produces a selective accumulation of longer chain MTXPGs that are known to be more potent inhibitors of de novo purine biosynthesis than shorter chain MTXPGs.

The impact of high-dose methotrexate on intracellular 6-mercaptopurine disposition during interval therapy of childhood acute lymphoblastic leukemia

PURPOSE

Low-dose methotrexate (MTX) therapy is the cornerstone treatment of acute lymphoblastic leukemia (ALL) and may enhance the activation of 6-mercaptopurine (6-MP) to 6-thioguanine nucleotides (6-TGN). Yet, data have established that high-dose MTX (HDMTX) hampers the accumulation of 6-TGN in red blood cells (RBC) and lymphoblasts.

METHODS

To clarify the pharmacokinetic interactions between these two antimetabolites, we serially measured RBC 6-TGN and MTX polyglutamates (MTXPG) levels following repeated courses of HDMTX (5 g/m(2) over 24 h) with daily oral 6-MP (25 mg/m(2)) during interval therapy in 20 children with ALL.

RESULTS

HDMTX produced a rapid reduction in RBC 6-TGN 24 h after the start of MTX, and this effect was sustained at least by the third day (median decrease -21%; P < 0.001). However, a return to pre-infusion of 6-TGN levels was observed by the time of the following HDMTX course 14 days later (P < 0.001). RBC MTX polyglutamates accumulation followed Michaelis-Menten kinetics but was not associated with the change in pre-infusion 6-TGN levels which remained stable during the interval period.

CONCLUSION

HDMTX does not appear to enhance 6-MP activation to 6-TGN. Moreover, given that the deleterious effect of HDMTX on intracellular 6-MP disposition has been shown to be several folds greater in lymphoblasts than in RBC. Our data warrant additional studies elucidating the optimal MTX dose synergizing with 6-MP.