The first modified Delphi consensus statement on sleeve gastrectomy.

INTRODUCTION: Sleeve gastrectomy (SG) is the commonest bariatric procedure worldwide. Yet there is significant variation in practice concerning its various aspects. This paper report results from the first modified Delphi consensus-building exercise on SG. METHODS: We established a committee of 54 globally recognized opinion makers in this field. The committee agreed to vote on several statements concerning SG. An agreement or disagreement amongst ≥ 70.0% experts was construed as a consensus. RESULTS: The committee achieved a consensus of agreement (n = 71) or disagreement (n = 7) for 78 out of 97 proposed statements after two rounds of voting. The committee agreed with 96.3% consensus that the characterization of SG as a purely restrictive procedure was inaccurate and there was 88.7% consensus that SG was not a suitable standalone, primary, surgical weight loss option for patients with Barrett's esophagus (BE) without dysplasia. There was an overwhelming consensus of 92.5% that the sleeve should be fashioned over an orogastric tube of 36-40 Fr and a 90.7% consensus that surgeons should stay at least 1 cm away from the angle of His. Remarkably, the committee agreed with 81.1% consensus that SG patients should undergo a screening endoscopy every 5 years after surgery to screen for BE. CONCLUSION: A multinational team of experts achieved consensus on several aspects of SG. The findings of this exercise should help improve the outcomes of SG, the commonest bariatric procedure worldwide, and guide future research on this topic.

Predicting Humoral Alloimmunity from Differences in Donor and Recipient HLA Surface Electrostatic Potential.

In transplantation, development of humoral alloimmunity against donor HLA is a major cause of organ transplant failure, but our ability to assess the immunological risk associated with a potential donor-recipient HLA combination is limited. We hypothesized that the capacity of donor HLA to induce a specific alloantibody response depends on their structural and physicochemical dissimilarity compared with recipient HLA. To test this hypothesis, we first developed a novel computational scoring system that enables quantitative assessment of surface electrostatic potential differences between donor and recipient HLA molecules at the tertiary structure level [three-dimensional electrostatic mismatch score (EMS-3D)]. We then examined humoral alloimmune responses in healthy females subjected to a standardized injection of donor lymphocytes from their male partner. This analysis showed a strong association between the EMS-3D of donor HLA and donor-specific alloantibody development; this relationship was strongest for HLA-DQ alloantigens. In the clinical transplantation setting, the immunogenic potential of HLA-DRB1 and -DQ mismatches expressed on donor kidneys, as assessed by their EMS-3D, was an independent predictor of development of donor-specific alloantibody after graft failure. Collectively, these findings demonstrate the translational potential of our approach to improve immunological risk assessment and to decrease the burden of humoral alloimmunity in organ transplantation.

Sensitization in Transplantation: Assessment of Risk (STAR) 2017 Working Group Meeting Report.

The presence of preexisting (memory) or de novo donor-specific HLA antibodies (DSAs) is a known barrier to successful long-term organ transplantation. Yet, despite the fact that laboratory tools and our understanding of histocompatibility have advanced significantly in recent years, the criteria to define presence of a DSA and assign a level of risk for a given DSA vary markedly between centers. A collaborative effort between the American Society for Histocompatibility and Immunogenetics and the American Society of Transplantation provided the logistical support for generating a dedicated multidisciplinary working group, which included experts in histocompatibility as well as kidney, liver, heart, and lung transplantation. The goals were to perform a critical review of biologically driven, state-of-the-art, clinical diagnostics literature and to provide clinical practice recommendations based on expert assessment of quality and strength of evidence. The results of the Sensitization in Transplantation: Assessment of Risk (STAR) meeting are summarized here, providing recommendations on the definition and utilization of HLA diagnostic testing, and a framework for clinical assessment of risk for a memory or a primary alloimmune response. The definitions, recommendations, risk framework, and highlighted gaps in knowledge are intended to spur research that will inform the next STAR Working Group meeting in 2019.

LILRB2 interaction with HLA class I correlates with control of HIV-1 infection.

Natural progression of HIV-1 infection depends on genetic variation in the human major histocompatibility complex (MHC) class I locus, and the CD8+ T cell response is thought to be a primary mechanism of this effect. However, polymorphism within the MHC may also alter innate immune activity against human immunodeficiency virus type 1 (HIV-1) by changing interactions of human leukocyte antigen (HLA) class I molecules with leukocyte immunoglobulin-like receptors (LILR), a group of immunoregulatory receptors mainly expressed on myelomonocytic cells including dendritic cells (DCs). We used previously characterized HLA allotype-specific binding capacities of LILRB1 and LILRB2 as well as data from a large cohort of HIV-1-infected individuals (N = 5126) to test whether LILR-HLA class I interactions influence viral load in HIV-1 infection. Our analyses in persons of European descent, the largest ethnic group examined, show that the effect of HLA-B alleles on HIV-1 control correlates with the binding strength between corresponding HLA-B allotypes and LILRB2 (p = 10(-2)). Moreover, overall binding strength of LILRB2 to classical HLA class I allotypes, defined by the HLA-A/B/C genotypes in each patient, positively associates with viral replication in the absence of therapy in patients of both European (p = 10(-11)-10(-9)) and African (p = 10(-5)-10(-3)) descent. This effect appears to be driven by variations in LILRB2 binding affinities to HLA-B and is independent of individual class I allelic effects that are not related to the LILRB2 function. Correspondingly, in vitro experiments suggest that strong LILRB2-HLA binding negatively affects antigen-presenting properties of DCs. Thus, we propose an impact of LILRB2 on HIV-1 disease outcomes through altered regulation of DCs by LILRB2-HLA engagement.

Impact of donor mismatches at individual HLA-A, -B, -C, -DR, and -DQ loci on the development of HLA-specific antibodies in patients listed for repeat renal transplantation.

We have analyzed the relationship between donor mismatches at each HLA locus and development of HLA locus-specific antibodies in patients listed for repeat transplantation. HLA antibody screening was undertaken using single-antigen beads in 131 kidney transplant recipients returning to the transplant waiting list following first graft failure. The number of HLA mismatches and the calculated reaction frequency of antibody reactivity against 10,000 consecutive deceased organ donors were determined for each HLA locus. Two-thirds of patients awaiting repeat transplantation were sensitized (calculated reaction frequency over 15%) and half were highly sensitized (calculated reaction frequency of 85% and greater). Antibody levels peaked after re-listing for repeat transplantation, were independent of graft nephrectomy and were associated with length of time on the waiting list (odds ratio 8.4) and with maintenance on dual immunosuppression (odds ratio 0.2). Sensitization was independently associated with increasing number of donor HLA mismatches (odds ratio 1.4). All mismatched HLA loci contributed to the development of HLA locus-specific antibodies (HLA-A: odds ratio 3.2, HLA-B: odds ratio 3.4, HLA-C: odds ratio 2.5, HLA-DRB1: odds ratio 3.5, HLA-DRB3/4/5: odds ratio 3.9, and HLA-DQ: odds ratio 3.0 (all significant)). Thus, the risk of allosensitization following failure of a first renal transplant increases incrementally with the number of mismatches at all HLA loci assessed. Maintenance of re-listed patients on dual immunosuppression was associated with a reduced risk of sensitization.

The efficacy of bariatric surgery performed in the public sector for obese patients with comorbid conditions.

OBJECTIVE: To determine the efficacy of bariatric surgery in the public sector for the treatment of complicated obesity. DESIGN, SETTING AND PARTICIPANTS: A longitudinal observational study of obese participants with comorbid conditions, aged 21-73 years, who underwent publicly funded bariatric surgery. Data were extracted from clinical databases (1 October 2009 to 1 September 2013) and recorded at seven time points. Participants are from an ongoing public obesity program. MAIN OUTCOME MEASURES: Postoperative weight loss and partial or full resolution of: type 2 diabetes mellitus (T2DM), hypertension (HTN), dyslipidaemia and obstructive sleep apnoea (OSA). RESULTS: The 65 participants in the cohort lost a mean weight of 22.6 kg (SD, 9.5 kg) by 3 months, 34.2.kg (SD, 20.1 kg) by 12 months and 39.9 kg (SD, 31.4 kg) by 24 months (P < 0.001). Body mass index (BMI) decreased from a preoperative mean of 48.2 kg/m(2) (SD, 9.5 kg/m(2)) to 35.7 kg/m(2) (SD, 7.7 kg/m(2)) by 24 months (P < 0.001). Full resolution of comorbid conditions by 18 months (P < 0.001) was achieved by almost half of those with baseline T2DM, nearly two-thirds with HTN and three-quarters of those with OSA, with continued improvements beyond 24 months. CONCLUSIONS: Bariatric surgery performed in the public sector is efficacious in the treatment of obese patients with comorbid conditions. Our findings parallel similar studies suggesting that there is equal benefit in publicly funded and privately performed procedures. This study highlights that obese patients reliant on public health care maintain sufficient intrinsic motivation in the absence of payment and supposed value-driven incentive. Improved access to bariatric surgery in the public sector can justifiably reduce the health inequities for those most in need.

Structural and electrostatic analysis of HLA B-cell epitopes: inference on immunogenicity and prediction of humoral alloresponses.

PURPOSE OF REVIEW: The immunogenic capacity of donor human leukocyte antigen (HLA) to induce humoral immune responses is not an intrinsic property of the mismatched alloantigen but depends on the HLA phenotype of the recipient. In recent years, advances in molecular sequence technology and information from X-ray crystallography have enabled structural comparison of donor and recipient HLA type providing an opportunity for a more rational approach for determining HLA compatibility. In this article, we review studies investigating the molecular basis of antibody-antigen interactions and present computational approaches to determine the complex physiochemical and structural properties of B-cell epitopes. RECENT FINDINGS: The relative immunogenicity of individual HLA mismatches may be predicted from analysis of polymorphic amino acids at continuous and discontinuous HLA sequence positions. The use of alloantigen sequence information alone, however, provides limited insight into key determinants of B-cell epitope immunogenicity, such as the orientation, accessibility and physiochemical properties of amino acid side chains. Advances in computational molecular modelling techniques now enable assessment of HLA-alloantibody interactions at the atomic level. Recent evidence supports a strong link between HLA B-cell epitope surface electrostatic potential and their immunogenicity. SUMMARY: Assessment of the surface electrostatic properties of HLA alloantigens and computational analyses of HLA-alloantibody interactions represent a promising area for future research into the molecular basis of HLA immunogenicity and antigenicity.

HLA class I allelic sequence and conformation regulate leukocyte Ig-like receptor binding.

Leukocyte Ig-like receptors (LILRs) are a family of innate immune receptors predominantly expressed by myeloid cells that can alter the Ag presentation properties of macrophages and dendritic cells. Several LILRs bind HLA class I. Altered LILR recognition due to HLA allelic variation could be a contributing factor in disease. We comprehensively assessed LILR binding to >90 HLA class I alleles. The inhibitory receptors LILRB1 and LILRB2 varied in their level of binding to different HLA alleles, correlating in some cases with specific amino acid motifs. LILRB2 displayed the weakest binding to HLA-B*2705, an allele genetically associated with several autoimmune conditions and delayed progression of HIV infection. We also assessed the effect of HLA class I conformation on LILR binding. LILRB1 exclusively bound folded ß(2)-microglobulin-associated class I, whereas LILRB2 bound both folded and free H chain forms. In contrast, the activating receptor LILRA1 and the soluble LILRA3 protein displayed a preference for binding to HLA-C free H chain. To our knowledge, this is the first study to identify the ligand of LILRA3. These findings support the hypothesis that LILR-mediated detection of unfolded versus folded MHC modulates immune responses during infection or inflammation.

Electrostatic modifications of the human leukocyte antigen-DR P9 peptide-binding pocket and susceptibility to primary sclerosing cholangitis.

UNLABELLED: The strongest genetic risk factors for primary sclerosing cholangitis (PSC) are found in the human leukocyte antigen (HLA) complex at chromosome 6p21. Genes in the HLA class II region encode molecules that present antigen to T lymphocytes. Polymorphisms in these genes are associated with most autoimmune diseases, most likely because they contribute to the specificity of immune responses. The aim of this study was to analyze the structure and electrostatic properties of the peptide-binding groove of HLA-DR in relation to PSC. Thus, four-digit resolution HLA-DRB1 genotyping was performed in 356 PSC patients and 366 healthy controls. Sequence information was used to assign which amino acids were encoded at all polymorphic positions. In stepwise logistic regressions, variations at residues 37 and 86 were independently associated with PSC (P = 1.2 × 10(-32) and P = 1.8 × 10(-22) in single-residue models, respectively). Three-dimensional modeling was performed to explore the effect of these key residues on the HLA-DR molecule. This analysis indicated that residue 37 was a major determinant of the electrostatic properties of pocket P9 of the peptide-binding groove. Asparagine at residue 37, which was associated with PSC, induced a positive charge in pocket P9. Tyrosine, which protected against PSC, induced a negative charge in this pocket. Consistent with the statistical observations, variation at residue 86 also indirectly influenced the electrostatic properties of this pocket. DRB1*13:01, which was PSC-associated, had a positive P9 pocket and DRB1*13:02, protective against PSC, had a negative P9 pocket. CONCLUSION: The results suggest that in patients with PSC, residues 37 and 86 of the HLA-DRß chain critically influence the electrostatic properties of pocket P9 and thereby the range of peptides presented.

On the road to single-site laparoscopic adjustable gastric banding: lessons learned from 60 cases.

BACKGROUND: Single-site laparoscopic surgery is a promising emerging technique with potential to decrease postoperative pain, reduce port-site complications, and improve cosmetic results. Laparoscopic adjustable gastric banding (LapGB) is a procedure that lends itself well to single-site laparoscopic surgery because the surgery is confined to a single region of the body, the need for a larger incision for port implantation and the fact that bariartric patients are more likely to be body image conscious. The procedure is, however, technically challenging and potentially more time consuming and hazardous. To simplify learning, a hybrid technique that used multiple conventional trocars and laparoscopic equipment through a single periumbilical incision while retaining the use of the Nathanson retractor via a separate epigastric incision was developed. The authors' experience and results with this technique are described. METHODS: This retrospective review describes the prospectively collected data for the first 60 consecutive cases completed using the minimally invasive technique described. RESULTS: The 60 cases in this study comprised 12 men and 48 women with an average age of 39 years (range 20-59 years). Their average body mass index (BMI) was 39.1 kg/m(2) (range 32-52 kg/m(2)). Four patients (6.7%) needed an additional port either for hemostasis or for access difficulties. Concomitant hiatal hernia repair was performed for 13 patients. Five patients (8.3%) had superficial wound infection requiring oral antibiotic therapy and dressings. No other complications were observed. Overall, the average operating time was 55 min (range 30-160 min). For both surgeons, the learning curve was six cases, with a significant difference in the operating times between the first six cases and the remaining cases (p < 0.0001, Mann-Whitney U test). CONCLUSIONS: The authors' early experience with the minimally invasive LapGB technique shows that it is feasible and safe. It can be used either as a bridging technique to single-site LapGB or on its own as a minimally invasive technique.

The First Modified Delphi Consensus Statement for Resuming Bariatric and Metabolic Surgery in the COVID-19 Times.

The purpose of this study was to achieve consensus amongst a global panel of expert bariatric surgeons on various aspects of resuming Bariatric and Metabolic Surgery (BMS) during the Coronavirus Disease-2019 (COVID-19) pandemic. A modified Delphi consensus-building protocol was used to build consensus amongst 44 globally recognised bariatric surgeons. The experts were asked to either agree or disagree with 111 statements they collectively proposed over two separate rounds. An agreement amongst ≥ 70.0% of experts was construed as consensus as per the predetermined methodology. We present here 38 of our key recommendations. This first global consensus statement on the resumption of BMS can provide a framework for multidisciplinary BMS teams planning to resume local services as well as guide future research in this area.

Association of the human leucocyte antigen region with susceptibility to Parkinson's disease.

OBJECTIVE: The core pathology of Parkinson's disease (PD) is a loss of the dopaminergic neurons in the nigro-striatal pathway, but this is only part of a more widespread pathological process, the nature of which is unknown. Recent data suggest a possible role for inflammation in this disease process. The Human Leucocyte Antigen (HLA) region is one of the most important genetic susceptibility factors in many immune-mediated diseases but has not been extensively investigated in PD. METHODS: The authors typed the HLA class II loci HLA-DRB1 and -DQB1 in 528 patients with Parkinson's disease and 3430 controls from the UK. RESULTS: The authors observed an association of HLA-DRB1 with susceptibility to Parkinson's disease. In particular, HLA-DRB1*03 was more common in patients compared with controls. CONCLUSIONS: These data suggest a possible role of the HLA region in susceptibility to Parkinson's disease and as such are consistent with other evidence supporting the role of an inflammatory process in the cellular loss in Parkinson's disease, especially of the nigral dopaminergic neurons.

Predicting the immunogenicity of human leukocyte antigen class I alloantigens using structural epitope analysis determined by HLAMatchmaker.

BACKGROUND: Human leukocyte antigen (HLA) matching strategies for kidney transplantation assign equal weighting to mismatches at a particular locus and take no account of variation in immunogenicity according to recipient HLA type. We examined the ability of intra- and interlocus analysis of amino-acid polymorphisms at continuous (triplet) and discontinuous positions (eplet) defined by the HLAMatchmaker program to predict alloantigen immunogenicity. METHODS: Sera from highly sensitized patients were screened for HLA class-I alloantibodies and mismatched combinations were analyzed using HLAMatchmaker to determine the number of triplet or extended-triplet and eplet mismatches. RESULTS: Logistic regression analysis revealed a strong correlation between the number of triplet or extended-triplet and eplet mismatches and both the presence and magnitude of alloantibody to mismatched HLA-A and -B specificities. The additional structural information provided by eplet analysis gave increased discrimination of mismatched-HLA specificities for alloantigens with greatest sequence disparity but this did not further improve the ability of triplet analysis to predict alloantigen immunogenicity. High antibody levels were observed for several mismatched-HLA combinations with zero triplet or eplet mismatches indicating that self triplets or eplets expressed in different conformations do not always predict nonimmunogenic epitopes. CONCLUSION: Analysis of recipient HLA type and mismatched-HLA alloantigens using the HLAMatchmaker algorithm allows prediction of immunogenic donor HLA types.

PECAM-1 polymorphism affects monocyte adhesion to endothelial cells.

BACKGROUND: Platelet endothelial cell adhesion molecule-1 (PECAM-1/CD31) plays an important role in leukocyte-endothelial cell adhesion and transmigration. Single nucleotide polymorphisms of PECAM-1 encoding amino acid substitutions at positions 98 leucine/valine (L/V), 536 serine/asparagine (S/N), and 643 arginine/glycine (R/G) occur in strong genetic linkage resulting in two common haplotypes (LSR and VNG). These PECAM-1 polymorphisms are associated with graft-versus-host disease after hematopoietic stem cell transplantation and with cardiovascular disease, but whether they influence PECAM-1 function is unknown. METHODS: We examined the effect of homozygous and heterozygous expression of the PECAM-1 LSR and VNG genotypes on the adhesive interactions of peripheral blood monocytes and activated endothelial cell monolayers under shear stress in a flow-based cell adhesion assay. RESULTS: There was no difference in monocyte adhesion between the two homozygous genotypes of PECAM-1 but when monocytes expressed both alleles in heterozygous form, firm adhesion of monocytes to endothelial cells was markedly increased. PECAM-1 polymorphism expressed in homozygous or heterozygous form by endothelial cells did not influence monocyte adhesion. CONCLUSIONS: This is, to our knowledge, the first demonstration that PECAM-1 genotype can alter the level of monocyte binding to endothelial cells and a demonstration that heterozygous expression of a polymorphic protein may lead to altered function.

Common bile duct polyp mimicking choledocholithiasis: a case report with laparoscopic transcystic management.

Although polyps of the extrahepatic biliary system are rare, an awareness of their potential existence is important as they may closely mimic choledocholithiasis clinically and radiologically but require distinct measures for successful management. This report describes the presentation and successful laparoscopic transcystic management of this infrequently encountered condition. It also explores the literature and discovers the numerous potential presenting features of common bile duct calculi and the spectrum of possible management options.

A Comparison of HLA Molecular Mismatch Methods to Determine HLA Immunogenicity.

BACKGROUND: Antibody-mediated rejection is a major cause of premature graft loss in kidney transplantation. Multiple scoring systems are available to assess the HLA mismatch between donors and recipients at the molecular level; however, their correlation with the development of de novo donor-specific antibody (dnDSA) has not been compared in recipients on active immunosuppression. METHODS: HLA-DRß1/3/4/5/DQα1ß1 molecular mismatch was determined using eplet analysis, amino acid mismatch, and electrostatic mismatch for 596 renal transplant recipients and correlated with HLA-DR/DQ dnDSA development. The molecular mismatch scores were evaluated in multivariate models of posttransplant dnDSA-free survival. RESULTS: Eplet mismatch correlated with amino acid mismatch and electrostatic mismatch (R = 0.85-0.96). HLA-DR dnDSA-free survival correlated with HLA-DR eplet mismatch (hazards ratio [HR], 2.50 per 10 eplets mismatched; P < 0.0001), amino acid mismatch (HR, 1.49 per 10 amino acids mismatched; P < 0.0001), and electrostatic mismatch (HR, 1.23 per 10 units mismatched; P < 0.0001). HLA-DQ dnDSA-free survival correlated with HLA-DQ eplet mismatch (HR, 1.98 per 10 eplets mismatched; P < 0.0001), amino acid mismatch (HR, 1.24 per 10 amino acids mismatched; P < 0.0001), and electrostatic mismatch (HR, 1.14 per 10 units mismatched; P < 0.0001). All 3 methods were significant multivariate correlates of dnDSA development after adjustment for recipient age, baseline immunosuppression, and nonadherence. CONCLUSIONS: HLA molecular mismatch represents a precise method of alloimmune risk assessment for renal transplant patients. The method used to determine the molecular mismatch is likely to be driven by familiarity and ease of use as highly correlated results are produced by each method.

Micromechanical adhesion force measurements between tetrahydrofuran hydrate particles.

Adhesion forces between tetrahydrofuran (THF) hydrate particles in n-decane were measured using an improved micromechanical technique. The experiments were performed at atmospheric pressure over the temperature range 261-275 K. The observed forces and trends were explained by a capillary bridge between the particles. The adhesion force of hydrates was directly proportional to the contact force and contact time. A scoping study examined the effects of temperature, anti-agglomerants, and interfacial energy on the particle adhesion forces. The adhesion force of hydrates was found to be directly proportional to interfacial energy of the surrounding liquid, and to increase with temperature. Both sorbitan monolaurate (Span20) and poly-N-vinyl caprolactam (PVCap) decreased the adhesion force between the hydrate particles.

Laparoscopic bile duct exploration: results of 160 consecutive cases with 2-year follow up.

BACKGROUND: Despite numerous reports showing the advantages of laparoscopic common bile duct exploration (LCBDE), many general surgeons, particularly those working outside of nonspecialist units, continue to rely heavily on endoscopic retrograde cholangiography with sphincterotomy (ERCP) to manage bile duct stones (BDS). This article investigates the performance of LCBDE when adopted as the preferred first-line management of both suspected and incidental BDS by general surgeons in a regional setting. METHODS: A retrospective review was conducted of all patients in whom LCBDE was attempted by a regional general surgical unit. The unit policy was to preferentially treat all incidental and suspected BDS (except in ascending cholangitis or severe pancreatitis) by LCBDE, with ERCP used only if unsuccessful. In addition to chart review, formal prospective follow up by telephone interview was carried out. RESULTS: A total of 160 consecutive patients with BDS (mean age 66.9 years, 65% suspected and 35% incidental) underwent attempted LCBDE between January 2000 and July 2005. Successful clearance was achieved in 84.3% according to chart review. However, four additional cases of retained choledocholithiasis shown by late telephone interview (median interval 2.5 years) yielded a more accurate clearance rate of 81.8%. Major morbidity occurred in 13.8%, including biliary leak in 7.5% and one late biliary stricture (0.6%). Median length of hospital stay was 4.8 days. In-hospital mortality was 0.6%. CONCLUSION: Laparoscopic common bile duct exploration remains an effective, efficient and safe first-line treatment of BDS even when carried out in regional nonspecialist units. In spite of the wide availability of ERCP, general surgeons should be encouraged to continue performing LCBDE in order to optimise patient care and maintain important surgical skills.

Technical Limitations of the C1q Single-Antigen Bead Assay to Detect Complement Binding HLA-Specific Antibodies.

BACKGROUND: Solid-phase assays to distinguish complement binding from noncomplement binding HLA-specific antibodies have been introduced, but technical limitations may compromise their interpretation. We have examined the extent to which C1q-binding to HLA-class I single-antigen beads (SAB) is influenced by denatured HLA on SAB, antibody titre, and complement interference that causes a misleading low assessment of HLA-specific antibody levels. METHODS: Sera from 25 highly sensitized patients were tested using Luminex IgG-SAB and C1q-SAB assays. Sera were tested undiluted, at 1:20 dilution to detect high-level IgG, and after ethylene diamine tetraacetic acid treatment to obviate complement interference. Conformational HLA and denatured HLA protein levels on SAB were determined using W6/32 and HC-10 monoclonal antibodies, respectively. Denatured HLA was expressed as HC-10 binding to untreated SAB as a percentage of maximal binding to acid-treated SAB. RESULTS: For undiluted sera, Luminex mean fluorescence intensity (MFI) values for IgG-SAB and C1q-SAB correlated poorly (r = 0.42). ethylene diamine tetraacetic acid and serum dilution improved the correlation (r = 0.57 and 0.77, respectively). Increasing levels of denatured HLA interfered with the detection of C1q binding. Consequently, the correlation between IgG-SAB MFI and C1q-SAB MFI was lowest using undiluted sera and SAB with greater than 30% denatured HLA (r = 0.40) and highest using diluted sera and SAB with 30% or less denatured HLA (r = 0.86). CONCLUSIONS: Antibody level, complement interference, and denatured HLA class I on SAB may all affect the clinical interpretation of the C1q-SAB assay. The C1q-SAB assay represents a substantial additional cost for routine clinical use, and we question its justification given the potential uncertainty about its interpretation.