Relevance of complement immunity with brain fog in patients with long COVID.

INTRODUCTION: This study aimed to elucidate the prevalence and clinical characteristics of patients with long COVID (coronavirus disease 2019), especially focusing on 50% hemolytic complement activity (CH50). METHODS: This retrospective observational study focused on patients who visited Okayama University Hospital (Japan) for the treatment of long COVID between February 2021 and March 2023. CH50 levels were measured using liposome immunometric assay (Autokit CH50 Assay, FUJIFILM Wako Pure Chemical Corporation, Japan); high CH50 was defined as ≥59 U/mL. Univariate analyses assessed differences in the clinical background, long COVID symptoms, inflammatory markers, and clinical scores of patients with normal and high CH50. Logistic regression model investigated the association between high CH50 levels and these factors. RESULTS: Of 659 patients who visited our hospital, 478 patients were included. Of these, 284 (59.4%) patients had high CH50 levels. Poor concentration was significantly more frequent in the high CH50 group (7.2% vs. 13.7%), whereas no differences were observed in other subjective symptoms (fatigue, headache, insomnia, dyspnea, tiredness, and brain fog). Multivariate analysis was performed on factors that could be associated with poor concentration, suggesting a significant relationship to high CH50 levels (adjusted odds ratio [aOR], 2.70; 95% confidence interval [CI], 1.33-5.49). Also, high CH50 was significantly associated with brain fog (aOR, 1.66; 95% CI, 1.04-2.66). CONCLUSIONS: High CH50 levels were frequently reported in individuals with long COVID, indicating a relationship with brain fog. Future in-depth research should examine the pathological role and causal link between complement immunity and the development of long COVID.

Combining maintenance therapy with hydroxychloroquine increases LLDAS achievement rates in individuals with stable systemic lupus erythematosus.

BACKGROUND: Hydroxychloroquine (HCQ) has been positioned as an anchor drug for systemic lupus erythematosus (SLE). There is evidence supporting the benefits of HCQ; however, the effect of additional HCQ in maintenance therapy remains unclear. METHODS: Thirty patients with SLE who visited Juntendo University Hospital were receiving maintenance therapy before HCQ treatment and were able to complete more than 104 weeks of HCQ treatment were analyzed. Anti-DNA antibody titers, IgG and CH50 levels, the maintenance dose of corticosteroids, the SLE disease activity index (SLEDAI), and the achievement of the Lupus Low Disease Activity State (LLDAS) were evaluated at baseline and at 12, 24, 52, and 104 weeks after HCQ initiation. RESULTS: We observed improvements in the anti-DNA antibody titers, IgG and CH50 levels, maintenance dose of corticosteroids, and SLEDAI at week 104 relative to baseline. Moreover, the LLDAS achievement rate increased over time from 10% at baseline to 43% and 80% at week 52 and week 104, respectively. CONCLUSION: Two years of continuous HCQ treatment led to improvements in SLE disease activity and corticosteroid dose and an increase in LLDAS achievement, thereby demonstrating the significance of the maintenance dose of HCQ for the management of SLE.

Method for Depletion of IgG and IgM from Human Serum as Naive Complement Source.

Understanding how human complement proteins interact with human antibodies is important for the development of antibody therapies and understanding autoimmune diseases. At present, many groups use baby rabbit serum as a source of complement because, in contrast to human serum, it lacks preexisting antibodies. However, for characterization of human (monoclonal) antibodies, human serum would be a preferred source of complement. To prevent complement activation via naturally occurring antibodies, this human serum ideally lacks IgG and IgM. Here we describe how to deplete human serum of naturally occurring IgG and IgM using fast protein liquid affinity chromatography (FPLC) while minimizing the loss of serum complement activity. We also describe assays that can be used to validate depletion of IgG and IgM (IgG, IgM, and C1q sandwich ELISAs) and functionally assess remaining serum complement activity (hemolytic assays CH50 and AH50). Finally, we demonstrate how captured IgG and IgM can be purified.

Hemolytic Tests Exploring Factor H Functional Activities.

Impairment of the complement regulatory protein Factor H (FH) is implicated in the physiopathological mechanisms of different diseases like atypical hemolytic and uremic syndrome and C3 glomerulopathies. It may be due to genetic abnormalities or acquired with the development of autoantibodies. FH has several ligands; therefore, the exploration of its functions requires to perform different tests. Among them, two hemolytic tests are very useful because they give specific and complementary information about FH functions. The first one is dedicated to explore the FH capacity to dissociate the alternative pathway C3 convertase, whereas the second one is designed to explore the capacity of FH to bind cell surfaces and to protect them from complement attack. This chapter describes the procedures to perform these two hemolytic tests, exploring in a complementary way the FH functionality.

Sheep Erythrocyte Preparation for Hemolytic Tests Exploring Complement Functional Activities.

Sheep erythrocytes (SE) are commonly used in complement functional tests. Non sensitized SE are useful to study the FH activity of cell protection. Indeed, as the cell surface of sheep erythrocytes is rich in sialic acids, Factor H (FH) is able to bind on it and therefore they represent a model of nonactivating surface. Because of their high capacity of complement regulation SE need to be modified to explore other functionality of the complement pathways, like the Complement hemolytic 50 (CH50) or the AP C3 convertase decay assays. For these tests, SE are sensitized with an anti-sheep red blood cell stroma antibody. In presence of serum or plasma complement components, sensitized SE may initiate complement cascade activation via the classic pathway explored in the CH50 assay. Sensitized SE may also be used to prepare C3b-coated SE that, with the use of buffers favoring AP, are suitable for the C3 Nef hemolytic assay and for the hemolytic assay studying the AP decay activity of FH. In this chapter we describe how to prepare SE for these different hemolytic tests.

Functional Hemolytic Test for Complement Alternative Pathway Convertase Activity.

The complement system is a key part of innate immunity. However, if the system becomes dysregulated, damage to healthy host cells can occur, especially to the glomerular cells of the kidney. The convertases of the alternative pathway of the complement system play a crucial role in complement activation. In healthy conditions, their activity is strictly regulated. In patients with diseases caused by complement alternative pathway dysregulation, such as C3 glomerulopathy and atypical hemolytic uremic syndrome, factors can be present in the blood that disturb this delicate balance, leading to convertase overactivity. Such factors include C3 nephritic factors, which are autoantibodies against the C3 convertase that prolong its activity, or genetic variants resulting in a stabilized convertase complex. This chapter describes a method in which the activity and stability of the alternative pathway convertases can be measured to detect aberrant serum factors causing convertase overactivity.

Detection of C3 Nephritic Factor by Hemolytic Assay.

C3 nephritic Factor (C3NeF) is autoantibody that binds neoepitopes of the C3 convertase C3bBb, resulting in a stabilization of the enzyme. First functional characterizations of C3NeF were performed by hemolytic assays using preactivated sheep erythrocytes (bearing C3b). Sheep erythrocytes are beforehand sensitized with an anti-sheep red blood cell stroma antibody produced in rabbit (hemolysin). Sensitized sheep erythrocytes will initiate cascade complement activation via the classic pathway, followed by alternative pathway amplification loop, resulting in C3b covalent binding to cell surface. Sheep erythrocytes bearing C3b permit the alternative pathway exploration, in particular decay of alternative pathway C3 convertase.

Lower CH50 as a predictor for intractable or recurrent lupus enteritis: A retrospective observational study.

OBJECTIVES: Lupus enteritis (LE) is a rare but well-known gastrointestinal manifestation of systemic lupus erythematosus (SLE). This study was conducted to identify prognostic factors associated with poor responses in patients with LE. METHODS: We consecutively registered patients diagnosed with LE between January 2009 and October 2019, and retrospectively compared their clinical characteristics based on whether they had good or poor responses to treatment. RESULTS: A total of 13 patients (17 episodes) were included. The median age was 41 years, and 12 patients were female. A comparison of clinical characteristics between groups revealed similar computed tomography (CT) findings. However, serum CH50 levels were significantly lower in the poor response group (median [interquartile ranges (IQR)]; 29.2 [25.3-46.9] U/mL vs 19.3 [7.8-24.0] U/mL, p = .0095). More patients in the poor response group had higher titers of anti-cardiolipin ß2-glycoprotein I antibody (anti-CL ß2GPI Ab) and were started on glucocorticoids (GCs) at moderate doses. In multivariable analysis, serum CH50 level was independently associated with poor response to induction therapy. CONCLUSION: Lower levels of CH50 at the time of initial treatment predicted inadequate treatment response in patients with LE.

Immune dyscrasia in adult growth hormone deficiency: Evaluation of hemolytic complement activity (CH50) and IgG subclasses.

CH50 is a screening assay for the activation of the classical complement pathway, the immunoglobulins-mediated one, activated in several inflammatory diseases. Adult growth hormone deficiency (aGHD) is recognized as a chronic inflammatory condition, although poorly evaluated under the profile of inflammatory biomarkers. The aim of this case-control observational study is to analyze CH50 and immunoglobulins G (IgG) subclasses production in aGHD, comparing this condition to healthy controls. 38 subjects were included and divided as follows: aGHD (n = 18, 6 females and 12 males); healthy controls (n = 20, 10 females and 10 males). GHD was diagnosed with dynamic test using Growth Hormone-Releasing Hormone (GHRH 50 µg i.v. + arginine 0,5 g/Kg), with a peak GH response < 9 µg/L when BMI was <30 kg/m2 or < 4 µg/L when BMI was >30 kg/m2. The two groups were evaluated for hormonal and metabolic parameters, CH50 and IgG subtypes. IgG1 and IgG2 were significantly higher in controls than in aGHD, while IgG3 and IgG4 showed a trend to higher levels in controls, although not significant. Furthermore, CH50 levels were significantly higher in aGHD. These data substantiate the hypothesis of a dyscrasia in IgG subclasses production in aGHD. As IgG levels decrease, CH50 levels do not.

Clinical implications of C6 complement component deficiency.

Background: Terminal complement component deficiencies are risk factors for neisserial infections. Objective: To review the clinical characteristics, the diagnosis and the management of patients with a terminal complement component deficiency. Methods: Pertinent articles were selected and reviewed in relation to a case presentation of C6 deficiency. Results: A case of a 56-year old patient with a history of meningitis, chronic rash, and C6 deficiency was presented, followed by discussion of clinical characteristics, diagnosis, and management of terminal complement component deficiencies. Clinical pearls and pitfalls were reviewed for the practicing allergist/immunologist and fellow-in-training. Conclusion: C6 deficiency is the most common terminal complement component deficiency and can present later in age with N. meningitidis infections. Patients can be screened for terminal complement component deficiency by checking CH50.

Refractory secondary thrombotic microangiopathy with kidney injury associated with systemic lupus erythematosus in a pediatric patient.

Thrombotic microangiopathy (TMA) is generally diagnosed through clinical features characterized as microangiopathic hemolytic anemia, thrombocytopenia, and multiple organ injury, as well as by pathological findings such as vascular damage and endothelial cell injury. Rheumatic and autoimmune diseases could be accompanied by secondary TMA; in fact, systemic lupus erythematosus (SLE) is a common disease associated with secondary TMA, and SLE complicated with TMA has been reported to have a poor prognosis. Although TMA occurs rarely in pediatric SLE patients, it often leads to severe clinical conditions. Here, we report a rare case of severe juvenile-onset SLE complicated with TMA and kidney injury. The 5-year-old patient showed renal dysfunction, thrombocytopenia, hemolytic anemia, nephrotic syndrome, hypocomplementemia, and elevation of anti-dsDNA IgG levels. Kidney biopsy revealed mesangial proliferation and endocapillary proliferation, as well as plumped endothelial cells, with full-house pattern deposits in immunofluorescence study. Combination treatment of methylprednisolone pulse therapy followed by oral prednisolone, mycophenolate mofetil, and plasma exchange was effective, whereas eculizumab did not show therapeutic effects. The patient further showed recurrent deterioration, and we initiated intravenous cyclophosphamide in addition to combination treatment and eventually succeeded in controlling the disease. Genome analysis by whole-exome sequencing revealed no particular gene mutation related to either complement disorders or type-1 interferon. Further elucidations concerning the pathogenic mechanisms causing juvenile-onset SLE are needed to establish an efficient treatment strategy for TMA with SLE.

[Frequency and titration of hemolytic activity of anti-A and anti-B antibodies in mothers of children with jaundice in Yaoundé, Cameroon]. / Fréquence et titrage des hémolysines anti-A et anti-B chez les mères d'enfants ictériques à Yaoundé, Cameroun.

INTRODUCTION: The alloimmunization of the ABO blood group system is involved in neonatal jaundice with a considerable overall prevalence. The role of ABO incompatibility is relatively little known. The purpose of this study was to investigate neonatal jaundice due to feto-maternal ABO incompatibilities and to determine the link between the hemolysins value in the mother and the degree of jaundice observed in the infant. METHODS: We conducted a cross-sectional study from June to November 2015. The study population was exclusively composed of moms who were blood type O with children who were a different blood type hospitalized in the Department of Neonatology at the Reference Hospital in the city of Yaoundé. Statistical analyses were performed using the GraphPadPrism 6 software with a confidence interval of 95%. RESULTS: Hemolysins frequency was of 20.58% (7/34) and anti-A hemolysin was the most common type (85.7%; 6/7). The new-born who had blood type B had a greater concentration of bilirubin levels compared to those of the AB group (p = 0.01). Multiparity was not associated with the presence of hemolysin (p = 0.8) as well as blood type of the infant was not associated with the occurrence of the hemolysins in the mother (p = 0.5). CONCLUSION: Early neonatal jaundice or protracted neonatal jaundice are also caused by hemolysins anti-A and anti-B derived from the allo-ABO immunization. A study on a larger sample is recommended for better assessment.

Temporal correlation between serum CH50 level and symptom severity of myasthenia gravis during eculizumab therapy.

The correlation between serum 50 % hemolytic complement (CH50) level and myasthenic symptom severity has not been known in patients with anti-acetylcholine receptor (anti-AChR)-positive myasthenia gravis (MG) during eculizumab treatment. A patient with anti-AChR-positive MG showed severe bulbar symptoms. Eculizumab administration decreased CH50 level and improved the symptoms. However, shortly after the second administration of eculizumab was postponed due to the development of pneumonia, his serum CH50 level returned almost to the level it was at before the initiation of eculizumab therapy and myasthenic symptoms worsened. Even after his pneumonia was completely cleared in response to an antibiotic, the severe myasthenic symptoms persisted. After eculizumab was resumed, serum CH50 level was reduced to below the limit of detection within 24 h, and the symptom steadily improved. His symptom severity was correlated temporally with serum CH50 level during eculizumab therapy. Our case suggests that serum CH50 level may be a marker of eculizumab-induced complement blockade and an indicator of a potential worsening of myasthenic symptoms during eculizumab treatment.

Complement Components sC5b-9 and CH50 Predict Prognosis in Heart Failure Patients Combined With Hypertension.

BACKGROUND: Heart failure (HF), resulting from inflammation and vessel injury, is one of the leading causes of poor quality of life and premature death. The complement system plays a leading role in vessel integrity and inflammation response. However, the association between serum complement level and the prognosis of HF remains unclear. METHODS: In our study, a total of 263 newly diagnosed hypertension patients with HF were included. Eight classical cardiovascular risk factors were collected, and plasma C3a, C3b, C5a, sC5b-9, and CH50 levels were detected. RESULTS: Compared with the control group, plasma C5a (P<0.001), sC5b-9 (P<0.001), and CH50 (P = 0.004) levels of hypertension patients with HF were significantly increased. On the basis of univariate analysis, an older age, higher frequency of alcohol consumption, high level of body mass index, medium or high risk of hypertension, hyperlipidemia, and diabetes were poor prognostic factors whereas low levels of C5a, sC5b-9, and CH50 were associated with favorable overall survival (OS). When these factors fit into a multivariate regression model, patients with hyperlipidemia (P = 0.002, hazard ratio [HR] = 3.09), N-terminal pro-Brain Natriuretic Peptide (NT-pro-BNP) ≥ 14.8 (P < 0.001, HR = 11.14), sC5b-9 level ≥ 1,406.2 µg/ml (P = 0.180, HR = 5.51) or CH50 level ≥ 294.6 µg/ml (P < 0.001, HR = 4.57) remained statistically factors for worsened OS and regarded as independent risk factors. These independently associated risk factors were used to form an OS estimation nomogram. Nomogram demonstrated good accuracy in estimating the risk, with a bootstrap-corrected C index of 0.789. CONCLUSIONS: sC5b-9 and CH50 levels are increased in hypertension patients with HF. Nomogram based on multivariate analysis has good accuracy in estimating the risk of OS.

Plasma Homocysteine Level Is Associated with the Expanded Disability Status Scale in Neuromyelitis Optica Spectrum Disorder.

BACKGROUND AND OBJECTIVE: Plasma homocysteine (Hcy) levels have been investigated among patients with multiple sclerosis (MS). However, the changes in Hcy levels and the association between Hcy levels and inflammatory/immune/cerebrospinal fluid (CSF) parameters in neuromyelitis optica spectrum disorder (NMOSD) patients have not been investigated yet. METHODS: Case data were collected from 97 acute-phase NMOSD patients and 39 stable-phase NMOSD patients. Patients in the acute phase were divided into 2 groups based on the EDSS score with cutoff equal to 4. Hcy levels, immunoglobulins (Ig) A, G, and M, complement 3 and 4, CH50, C-reactive protein, erythrocyte sedimentation rate (ESR), and CSF examination including white blood cells and total protein were determined. RESULTS: No significant differences in Hcy levels are observed between acute-phase and stable-phase NMOSD patients. Hcy and ESR levels were significantly higher in acute-phase NMOSD patients with EDSS score ≥4. Besides, EDSS is positively correlated with Hcy level, ESR, 1/aquaporin-4 titer and Hcy level is negatively correlated with IgM in acute-phase NMOSD patients. CONCLUSION: Elevated plasma Hcy has the potential to affect the pathogenesis or progression of NMOSD.

Cryoglobulins Today: Detection and Immunologic Characteristics of 1,675 Positive Samples From 13,439 Patients Obtained Over Six Years.

OBJECTIVE: Cryoglobulins are cold-precipitating immunoglobulins. Through progress in techniques, we undertook this study to update information on the biologic characteristics of cryoglobulins in a very large population. METHODS: A cohort of 13,439 patients was tested for cryoglobulins from January 2010 to December 2016. The analysis included cryoglobulin isotype, clonality, concentration, and IgM rheumatoid factor (IgM-RF) in cryoprecipitate, as well as serum complement and RF. Markers of gammopathy, viral infection, and autoimmunity were also investigated. RESULTS: Of the 13,439 patients, 1,675 (12.5%) tested positive for cryoglobulins: 155 patients (9.3%) with type I, 788 (47%) with type II, and 732 (43.7%) with type III cryoglobulins. Nine percent of patients who were retested after initially testing negative for cryoglobulins showed a positive result on a follow-up test (196 of the 2,213 retested patients). In type I cryoglobulins, IgM was more frequent but occurred at lower concentrations than IgG. Mixed cryoglobulins were found in 34.8% of the tested patients who were positive for hepatitis C virus and <5% of those who were positive for hepatitis B virus or HIV. Of the patients with anti-double-stranded DNA, anti-SSA, or anti-cyclic citrullinated peptide autoantibodies, 25.4% tested positive for mixed cryoglobulins, with type III occurring more frequently than type II. Both cryoprecipitate and serum were RF-positive in 21.6% of type II and 10.1% of type III cryoglobulins. A decrease of C4, with or without accompanying decreases of C3 and CH50, was found in 23.6% of cryoglobulin samples. CONCLUSION: Obtained with the use of modern assays, our findings from this very large collection of cryoglobulins provide an update on cryoglobulin distribution and characteristics, with minimal selection bias. Despite strict preanalytical conditions, a negative finding for the presence of cryoglobulin must be confirmed in a second sample. RF activity and complement decreases were rarely detected.

Diagnostic Utility of Complement Serology for Atypical Hemolytic Uremic Syndrome.

OBJECTIVE: To investigate the clinical utility of a 9-analyte complement serology panel (COMS) covering complement function (CH50 and AH50), components (C3, C4), factor B (CFB), factor H, and activation markers (C4d, Bb, and soluble membrane attack complex) for the diagnosis of atypical hemolytic uremic syndrome (aHUS). METHODS: Physician orders for COMS from January 19, 2015, through November 4, 2016, were reviewed. Demographic characteristics, patient diagnosis, and laboratory parameters were recorded. RESULTS: There were 177 COMS orders for 147 patients. The median patient age was 44.9 years (range, 0.9-88.0 years). Common reasons for ordering COMS included monitoring and diagnosis of C3 glomerulopathy and renal dysfunction and differentiation of aHUS from other thrombotic microangiopathies (TMAs). Forty-four patients had COMS ordered for TMAs: 8 had aHUS and all had 1 or more abnormalities within the alternative pathway of complement. Although the sensitivity of this finding for the diagnosis of aHUS is 100%, the specificity is only 28%, with a positive likelihood ratio of 1.39. Patients with aHUS had lower CH50, C3, and CFB than did those with secondary non-aHUS TMA (all P<.01). A combined CFB of 20.9 mg/dL or less and CH50 of 56% or less led to sensitivity of 75% with increased specificity of 88.9% and a diagnostic odds ratio of 24. CONCLUSION: A COMS abnormality should not be interpreted in isolation. In conjunction with clinical presentation, a decrease in both CFB and CH50 may be an important clue to support the diagnosis of aHUS.

Cut-off values of immunological tests to identify patients at high risk of severe lupus nephritis.

Cut-off values for anti-dsDNA, anti-nucleosome and anti-C1q antibodies tests and for complementmediated hemolytic activity (CH50) were explored to identify patients with high risk of developing severe lupus nephritis (LN). Forty-one patients with confirmed systemic lupus erythematosus (SLE) were identified; their levels for the three antibodies and complement had been measured on a same serum sample. These patients were classified based on the presence of renal involvem ent; sixteen had active proliferative LN. With the cut-off values accepted in the laboratory for SLE diagnosis (anti-dsDNA > 100 UI/ml, anti-nucleosome > 50 U/ml or CH50 < 190 UCH50%) no significant differences were found between patients with and without LN. Anti-C1q > 40 U/ml showed a statistically significant association with LN and had 80% of specificity. Cut-off values for LN identified by Receiver Operating Characteristic curves (ROC) were higher for anti-dsDNA (> 455 IU/ml) and antinucleosome (>107 U/ml), lower for CH50 (< 150 UCH50%) and, for anti-C1q (> 41 U/ml) coincided with the cut-off values accepted for SLE. Anti-C1q > 134 U/ml had a 92% of specificity, 56% of sensibility and was associated with a fifteen-fold increased risk of LN. The simultaneous presence of anti-nucleosome > 107 U/ml and anti-C1q > 134 U/ml was associated with a 27-fold higher probability for LN. According to these results, the cut-off values used to detect SLE activity could be inadequate to identify patients at high risk of severe LN.

Cut-off values of immunological tests to identify patients at high risk of severe lupus nephritis

Cut-off values for anti-dsDNA, anti-nucleosome and anti-C1q antibodies tests and for complement-mediated hemolytic activity (CH50) were explored to identify patients with high risk of developing severe lupus nephritis (LN). Forty-one patients with confirmed systemic lupus erythematosus (SLE) were identified; their levels for the three antibodies and complement had been measured on a same serum sample. These patients were classified based on the presence of renal involvem ent; sixteen had active proliferative LN. With the cut-off values accepted in the laboratory for SLE diagnosis (anti-dsDNA > 100 UI/ml, anti-nucleosome > 50 U/ ml or CH50 < 190 UCH50%) no significant differences were found between patients with and without LN. Anti-C1q > 40 U/ml showed a statistically significant association with LN and had 80% of specificity. Cut-off values for LN identified by Receiver Operating Characteristic curves (ROC) were higher for anti-dsDNA (> 455 IU/ml) and anti-nucleosome (>107 U/ml), lower for CH50 (< 150 UCH50%) and, for anti-C1q (> 41 U/ml) coincided with the cut-off values accepted for SLE. Anti-C1q > 134 U/ml had a 92% of specificity, 56% of sensibility and was associated with a fifteen-fold increased risk of LN. The simultaneous presence of anti-nucleosome > 107 U/ml and anti-C1q > 134 U/ml was associated with a 27-fold higher probability for LN. According to these results, the cut-off values used to detect SLE activity could be inadequate to identify patients at high risk of severe LN.

Se exploraron valores de corte para los ensayos de anti-ADNdc, anti-nucleosoma, anti-C1q y complemento hemolítico total (CH50) capaces de identificar los casos con mayor riesgo de nefritis lúpica (NL) grave. Se seleccionaron 41 pacientes ≥ 16 años con lupus eritematoso sistémico (LES) confirmado que tenían titulados los niveles de los tres anticuerpos y CH50, en una misma muestra de suero. Fueron clasificados según presencia de compromiso renal; 16 presentaron formas proliferativas de NL activa. Con los valores de corte aceptados por el laboratorio para el diagnóstico de LES (anti-ADNdc > 100 UI/ml, anti-nucleosoma > 50 U/ml o un CH50 < 190 UCH50%) no se encontraron diferencias significativas entre casos con y sin NL. Un anti-C1q > 40 U/ml tuvo una especificidad del 80% y mostró una asociación estadísticamente significativa con NL. Al aplicar curvas Receiver Operating Characteristic (ROC) para NL, se identificaron valores de corte más altos para anti-ADNdc (> 455 IU/ml) y anti-nucleosoma (> 107 U/ml), más bajo para CH50 (< 150 UCH50%) y para el anti-C1q (> 41 U/ml) coincidió con el aceptado para diagnóstico de LES. Un anti-C1q > 134 U/ml presentó una sensibilidad del 56%, una especificidad del 92% y se asoció con quince veces más riesgo de NL. La presencia simultánea de anti-C1q > 134 U/ml y anti-nucleosoma > 107 U/ml se asoció 27 veces más riesgo de NL. De acuerdo a estos resultados los valores de corte empleados para actividad en pacientes con LES podrían resultar inadecuados para identificar pacientes con mayor riesgo de NL grave.