C-reactive protein in juvenile chronic arthritis: an indicator of disease activity and possibly amyloidosis

C-Reactive Protein: Pathophysiology, Diagnosis, False Test Results and a Novel Diagnostic Algorithm for Clinicians

The current literature provides a body of evidence on C-Reactive Protein (CRP) and its potential role in inflammation. However, most pieces of evidence are sparse and controversial. This critical state-of-the-art monography provides all the crucial data on the potential biochemical properties of the protein, along with further evidence on its potential pathobiology, both for its pentameric and monomeric forms, including information for its ligands as well as the possible function of autoantibodies against the protein. Furthermore, the current evidence on its potential utility as a biomarker of various diseases is presented, of all cardiovascular, respiratory, hepatobiliary, gastrointestinal, pancreatic, renal, gynecological, andrological, dental, oral, otorhinolaryngological, ophthalmological, dermatological, musculoskeletal, neurological, mental, splenic, thyroid conditions, as well as infections, autoimmune-supposed conditions and neoplasms, including other possible factors that have been linked with elevated concentrations of that protein. Moreover, data on molecular diagnostics on CRP are discussed, and possible etiologies of false test results are highlighted. Additionally, this review evaluates all current pieces of evidence on CRP and systemic inflammation, and highlights future goals. Finally, a novel diagnostic algorithm to carefully assess the CRP level for a precise diagnosis of a medical condition is illustrated.

α2-fraction and haptoglobin as biomarkers for disease activity in oligo- and polyarticular juvenile idiopathic arthritis

OBJECTIVES

Unlike in adult rheumatology, for most forms of juvenile idiopathic arthritis (JIA) no reliable biomarkers currently exist to assess joint and disease activity. However, electrophoresis is frequently found changed in active juvenile arthritis. The objective of this study was to evaluate the α2-fraction of serum electrophoresis and its main components as biomarkers for JIA, categories extended/persistent oligoarthritis and seronegative polyarthritis, in comparison with the conventionally used erythrocyte sedimentation rate and C-reactive protein.

METHODS

Serum samples and clinical data from 181 patients with JIA were collected. Serum electrophoresis and α2-fraction and its components were determined using standard methods. Relationship between calculated α2-fraction of serum electrophoresis (CA2F) and its components, acute-phase parameters and cJADAS27 was assessed using Pearson's correlation coefficient and linear regression modelling, adjusting for confounding effects. Results were confirmed in a second cohort with 223 serum samples from 37 patients, using a mixed model to account for repeated measures.

RESULTS

Compared to ESR and CRP, CA2F showed higher correlation to cJADAS27, in particular for persistent oligoarthritis. Of the three components of the α2-fraction, haptoglobin showed the highest correlation to cJADAS27. Regression analysis demonstrated higher ability to predict cJADAS27 for CA2F, and especially for haptoglobin as a component thereof, than for CRP and ESR.

CONCLUSION

Compared to conventional methods, α2-fraction of serum electrophoresis and specifically, haptoglobin show higher correlations with disease activity in common subtypes of JIA, representing excellent candidates as biomarkers for disease activity. Further studies are necessary to determine diagnostic value and correlations in other subtypes.

Plasma interleukin-37 is increased and inhibits the production of inflammatory cytokines in peripheral blood mononuclear cells in systemic juvenile idiopathic arthritis patients

Background

Interleukin (IL)-37 has emerged as a novel anti-inflammatory cytokine that play an immunosuppressive role in regulating inflammatory response. This study aimed to measure IL-37 levels in the plasma and peripheral blood mononuclear cells (PBMCs) of patients with systemic juvenile idiopathic arthritis (sJIA), and to establish the correlation between IL-37 levels and disease activity, laboratory parameters and inflammatory cytokines.

Methods

The mRNA levels of IL-37 in PBMCs and plasma IL-37 concentrations in 46 sJIA patients and 30 age- and sex-matched healthy controls were measured by real-time polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA), respectively. The correlations between plasma IL-37 levels and disease activity, laboratory parameters and inflammatory cytokines in sJIA were analyzed by Spearman correlation test. PBMCs from the sJIA patients were stimulated with recombinant human IL-37 (rhIL-37) protein, expressions of IL-1β, IL-6, TNF-α and IL-17 were detected by RT-PCR and ELISA.

Results

Plasma levels of IL-37 and relative IL-37 mRNA expression were significantly elevated in sJIA patients, especially in active sJIA patients, when compared with the healthy controls (P < 0.001). Furthermore, patients with active disease showed higher IL-37 mRNAs and plasma protein levels than those with inactive disease as well as healthy controls. Plasma IL-37 levels were correlated with disease activity and inflammatory cytokines (IL-6, TNF-α, IL-17 and GM-CSF) in sJIA patients. The productions of inflammatory cytokines such as IL-6, TNF-α, IL-17 in PBMCs from sJIA patients were obviously decreased after recombinant IL-37 stimulation, whereas the production of IL-1β was not changed.

Conclusions

Our results demonstrate that levels of IL-37 were higher in sJIA patients, which were correlated with disease activity and sJIA related inflammatory cytokines. In addition, rhIL-37 down-regulates the expressions of inflammatory cytokines form PBMCs in sJIA patients, suggesting that IL-37 may have the potential role as a natural inhibitor for the pathogenesis and therapy of sJIA.

Electronic supplementary material

The online version of this article (10.1186/s12967-018-1655-8) contains supplementary material, which is available to authorized users.

Laboratory testing in pediatric rheumatology

In children, laboratory evaluations can assist in the screening of patients for inflammatory disorders, confirm diagnoses, allow for monitoring of disease activity and response to therapy, and suggest prognoses and risk of morbidities associated with rheumatic diseases. This review provides an overview of the usefulness and interpretation of both the commonly ordered tests ordered by the general pediatrician as well as those frequently used in the pediatric rheumatology clinic for diagnosis and disease monitoring. Studies discussed include the complete blood count, acute phase reactants, autoantibodies, serum complement, urinalysis, streptococcal antibody tests, and commonly used genetic studies.

Cryopyrin-associated periodic syndrome: an update on diagnosis and treatment response

Cryopyrin-associated periodic syndrome (CAPS) is a rare hereditary inflammatory disorder encompassing a continuum of three phenotypes: familial cold autoinflammatory syndrome, Muckle-Wells syndrome, and neonatal-onset multisystem inflammatory disease. Distinguishing features include cutaneous, neurological, ophthalmologic, and rheumatologic manifestations. CAPS results from a gain-of-function mutation of the NLRP3 gene coding for cryopyrin, which forms intracellular protein complexes known as inflammasomes. Defects of the inflammasomes lead to overproduction of interleukin-1, resulting in inflammatory symptoms seen in CAPS. Diagnosis is often delayed and requires a thorough review of clinical symptoms. Remarkable advances in our understanding of the genetics and the molecular pathway that is responsible for the clinical phenotype of CAPS has led to the development of effective treatments. It also has become clear that the NLRP3 inflammasome plays a critical role in innate immune defense and therefore has wider implications for other inflammatory disease states.

Laboratory tests in the diagnosis and follow-up of pediatric rheumatic diseases: an update

OBJECTIVES

We reviewed the literature to evaluate the role of common laboratory tests and to examine the recent progress in the laboratory diagnosis of pediatric rheumatic diseases.

METHODS

We used the PubMed database (1950-2008) to search for the keywords "laboratory," "erythrocyte sedimentation rate" (ESR), "C-reactive protein" (CRP), "blood cytology," "procalcitonin" (PCT), "complement system," "ferritin," "antistreptolysin O titer" (ASO), "autoantibodies," "genetic studies," in conjunction with "rheumatic disease in children" and "pediatric autoimmune diseases." All relevant original and review articles in English were reviewed as well as textbooks of pediatric rheumatology.

RESULTS

Laboratory tests (ESR, CRP, blood cytology, complement system, ferritin, ASO titer) play an important role in confirming a diagnosis and in the follow-up of rheumatic diseases in the pediatric age group. The ESR is probably the most widely measured index of the acute phase response. Measurement of CRP is very useful in the rapid diagnosis of infection as a progressive increase can be shown in the first 48 hours. Also, the subsequent fall in serum CRP concentration on resolution of inflammation is useful for monitoring the efficacy of treatment. In chronic diseases, a combination of CRP and ESR may provide the most useful information. Cytopenia and different forms of anemia can be encountered in many rheumatic diseases: they can be related to disease activity or to therapeutic side effects. Determination of complement levels (C3 and/or C4) is useful in the follow-up of systemic lupus erythematosus (SLE) and membranoproliferative glomerulonephritis. Ferritin is a laboratory hallmark of primary and secondary hemophagocytic lymphohistiocytosis. ASO titer should be obtained to confirm a diagnosis of acute rheumatic fever; other important antibody markers of streptococcal infection include antihyaluronidase, antideoxyribonuclease B, and antistreptokinase antibodies. We also found that, in the pediatric age, the main indication for synovial fluid analysis is suspected joint infection. Antinuclear antibodies, anti-Smith antigen, and anti-double-stranded DNA antibodies are important in the diagnosis of SLE, are useful prognostic markers, and facilitate clinical and treatment follow-up. Anti-SSA/Ro and anti-SSB/La antibodies are associated with Sjögren's syndrome and congenital heart block, while the anti-U1 small nuclear ribonucleoprotein antibodies show high specificity for mixed connective tissue disease. Repetitive spontaneous abortions, thrombocytopenia, and many types of venous or arterial thrombosis are associated with antiphospholipid antibodies. The presence of cytoplasmic antineutrophil antibodies is essential in the diagnosis of Wegener granulomatosis. The discovery of underlying single causative gene defects led to the identification of several autoinflammatory diseases, a group of genetic disorders characterized by recurrent attacks of inflammation (hereditary periodic fever syndromes). These include familial Mediterranean fever due to mutations in the Mediterranean fever (MEFV) gene, hyperimmunoglobulinemia D syndrome due to mutations in the MK gene for mevalonate kinase, cryopyrinopathies such as Muckle-Wells syndrome or neonatal-onset multisystemic inflammatory disease (neonatal-onset multisystemic inflammatory disease or chronic infantile neurological cutaneous and articular (CINCA)) associated with cold-induced autoinflammatory syndrome 1 gene mutations, and tumor necrosis factor receptor-associated periodic syndrome due to mutation of TNF receptor I gene.

CONCLUSIONS

Laboratory investigations play an important role in the diagnosis and follow-up of inflammatory rheumatic diseases in children. A good history and a complete physical examination are the best screening tests. Routine laboratory tests are useful to confirm a suspected diagnosis, to assess disease activity, and to measure the response and toxicity to treatment. Only a few tests represent diagnostic criteria such as antinuclear antibodies and anti-double-stranded DNA in SLE or cytoplasmic antineutrophil cytoplasmic autoantibodies in Wegener's granulomatosis. Recent advances in molecular genetics have impacted diagnosis, pathogenesis, and treatment in genetic fever syndromes.

Systemic onset juvenile rheumatoid arthritis

Systemic onset juvenile rheumatoid arthritis (SoJRA) accounts for 10-20% of all JRA, affecting males and females equally and occurring most frequently under the age of 5 years. It is characterized by arthritis, daily spiking fever, an evanescent rash, serositis and a variety of other extra-articular features. Exclusion of systemic infections, malignancies and connective tissue diseases is most important in establishing the diagnosis. The disease has a wide range of severity from a short monocyclic course to a prolonged chronic course with severe destructive arthritis in approximately one third of patients. Destructive arthritis, secondary amyloidosis and treatment complications including infections, osteoporosis, growth retardation and the macrophage activation syndrome account for the significant morbidity and mortality associated with the disease. Pharmacological management includes non-steroidal anti-inflammatory drugs, corticosteroids, methotrexate and an emerging role for cyclosporine A and cytotoxic drug therapy. Elucidation of the immunopathogenetic mechanisms may lead to new targeted therapy.

The effect of methotrexate and azathioprine on the serum levels of IgA-alpha 1-antitrypsin complex in juvenile chronic arthritis

In the present study we investigated the influence of methotrexate (MTX) and azathioprine (AZA) on the serum levels of the IgA-alpha 1-antitrypsin (IgA-AT) complex in patients with the systemic form of juvenile chronic arthritis (JCA). Fifty-six JCA patients (22 treated with MTX, 18 treated with AZA, and 16 not treated with any immunosuppressive agent) were enrolled in the study. MTX dosage ranged from 0.3 to 0.5 mg/kg-1 week-1, while AZA was given daily at an average dose of 1 mg/kg. MTX was given for 13 months (SD = 7 months) whereas AZA for 11 months (SD = 6 months). The average value of the complex was higher in JCA patients than in both control groups (0.74 +/- 0.73 U vs 0.37 +/- 0.13 U (control children), P < 0.001 and vs 0.23 +/- 0.12 U (control adults), P < 0.001). Values exceeding the normal range were found in twenty-two JCA patients (39.4%). Serum IgA-AT level was lowest in the MTX group compared to AZA and non-treated patients (0.56 +/- 0.24 U, 0.76 = 0.43 U, 0.95 +/- 0.52 U, respectively, P < 0.05). IgA values exceeding normal levels for age were found in 14% of the patients. A correlation between the levels of the IgA-AT complex and C-reactive protein (r = 0.43, P < 0.01), alpha 1-acid-glycoprotein (r = 0.45, P < 0.01), alpha 1-antichymotrypsin (r = 0.52, P < 0.01), alpha 1-antitrypsin (r = 0.40, P < 0.01) and IgA (r = 0.56, P < 0.01) was established.

Acute phase proteins in the monitoring of inflammatory disorders

The acute phase reaction is in most circumstances a good indicator of (local) inflammatory activity and tissue damage. CRP is a direct and quantitative measure for the acute phase reaction and due to its fast kinetics provides adequate information of the actual situation. The ESR on the contrary is in fact an indirect measure of the acute phase reaction. It does react much slower to changes of inflammatory activity and is influenced by a number of other factors. From studies on the 'behaviour' of CRP it has become clear that diseases may differ with regard to the extent in which they induce an acute phase response. Incidental measurement of the CRP level may add to the diagnostic procedure in selected cases, e.g. in the differentiation between a bacterial and a viral infection or between a bacterial infection and an exacerbation of diseases like SLE. In case of an extremely elevated CRP level (> 100 mg/litre) the possibility of a bacterial infection should always be considered. In clinical practice CRP is particularly useful when serial measurements are performed. The course of the CRP level may be useful for the monitoring of the effect of treatment and for the early detection of postoperative complications or intercurrent infections. The relationship between CRP and the local production and effects of cytokines on the one hand, and the possible functional role of CRP in the inflammatory process on the other hand have surely added a dimension to the clinical use of CRP as a parameter of inflammatory activity.

Fever of unknown origin in childhood: difficulties in diagnosis

We have described a child with systemic onset juvenile chronic arthritis who presented initially with fever of unknown origin. Treatment of a presumed infection led to a severe allergic response with Stevens-Johnson syndrome, renal failure and DIC. This reaction obscured the features of the underlying disease and delayed the diagnosis.

Acute phase reactants in predicting disease outcome

From the studies which are reviewed above, it is generally apparent that in terms of the acute phase response, the initial findings in early inflammatory arthritis (particularly rheumatoid arthritis, with which the majority of such studies are concerned) have little predictive value for either the functional outcome or mortality. The wide interindividual variability in these measurements is also likely to limit their clinical usefulness as predictors of disease outcome. The trend in certain acute phase reactants may be more useful in indicating disease activity, although the number of satisfactory studies in this area is very limited.

Correlation of serum interleukin-6 levels with joint involvement and thrombocytosis in systemic juvenile rheumatoid arthritis

We measured interleukin-6 (IL-6) levels in 70 serum samples obtained from 25 patients with systemic-onset juvenile rheumatoid arthritis (JRA), using the hybridoma cell line B9. Patients with systemic-onset JRA had significantly elevated serum IL-6 levels during active disease (mean +/- SD 92.1 +/- 75.1 hybridoma growth factor units/ml; P less than 0.00001 versus healthy age-matched controls), but not during remission. Serum IL-6 levels correlated with the extent and severity of joint involvement (P less than 0.001) and with platelet counts (P less than 0.05). Our data suggest that IL-6 plays a significant role in the pathogenesis of systemic-onset JRA.

C-reactive protein in the assessment of disease activity in juvenile rheumatoid arthritis and juvenile spondyloarthritis

Disease activity in 31 children with JRA and 12 with JSA was investigated clinically and by serial measurements of serum CRP and ESR over a one-year period. Prior mean duration of disease was 4.3 years. There was a significant correlation of CRP with ESR and both parameters correlated significantly with clinical disease activity. CRP concentrations and ESR in active disease were significantly higher than in moderately active and inactive disease, though neither parameter showed any significant difference between moderately active and inactive disease. Clinical scoring was more sensitive in detection of moderate disease activity than were CRP and ESR. However, in systemic JRA without articular involvement, laboratory parameters were more useful for assessing disease activity.

A solid-phase enzyme immunoassay for C-reactive protein: clinical value and the effect of rheumatoid factor

Measurement of serum C-reactive protein (CRP) concentration is useful in monitoring the progress of chronic inflammatory diseases. Rheumatoid factor, by its interaction with the Fc portion of IgG, has the potential to interfere with solid-phase immunoassays for CRP and other serum proteins. To determine the effect of RF on a solid-phase enzyme immunoassay for CRP we compared assays employing whole antisera or F(ab')2 fragments. In 92 sera with RF latex titres ranging from 1/80 to 1/81,920, no correlation was found between RF concentrations and CRP measurements. CRP concentrations measured by use of whole antisera (mean +/- standard error of the mean, 59.7 +/- 5.7 mg/l, n = 92) were lower than those measured with F(ab')2 fragments (62.5 +/- 5 mg/l), indicating that exaggeration of CRP measurements did not occur in RF containing sera under the conditions of the assay. Our results show that in the CRP-ELISA, interference from RF was precluded by the high serum dilutions employed. At lower serum dilutions RF binding was detected. Consequently, in solid-phase enzyme immunoassays at lower serum dilutions the presence of RF may lead to false positive results and exaggerated measurements.