Laboratory marker profile of patients with Juvenile Idiopathic Arthritis in a paediatric rheumatology outpatient clinic service at Tygerberg Hospital
Date
2020-12
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Stellenbosch : Stellenbosch University
Abstract
ENGLISH ABSTRACT: Background:
Juvenile idiopathic arthritis (JIA) is the most commonly occurring chronic rheumatic disease of childhood. The diagnosis is currently a clinical one with Rheumatoid factor and HLA-B27 antigen as the only laboratory markers included in the International League of Associations for Rheumatology’s classification (ILAR).
Aim:
The primary aim of the study was to examine the laboratory marker profile of patients with JIA at entry into the clinic. The secondary aim was to describe the distribution of the profile in the 7 JIA subgroups.
Method:
A retrospective, descriptive study was done at Tygerberg Hospital. It included all patients who met the diagnostic criteria (ILAR) for JIA seen at the paediatric rheumatology clinic between the clinic’s inception in 1995 to July 2017. Exclusion criteria were an age older than 16 years, HIV infection or another rheumatological condition.
Results:
A total of 165 patients were recorded, with an overall predominance of female gender (58.2%), however for the subgroups of Enthesitis Related JIA, Psoriatic JIA and unspecified JIA there was a higher male to female ratio. Polyarticular JIA at 39% made up the largest subgroup, of which 15.8% were classified as poly RF positive and 23.6% as poly RF negative, closely followed by Oligoarthritis JIA, which made up 23% and which also had the youngest median age of presentation at 5 years (IQR 2-8) and 31.4% had positive antinuclear antigen (ANA). ANA positivity across the other subgroups was 23% for poly RF positive, 7.9% for poly RF negative, 8% for systemic JIA, 5% enthesitis related JIA, 100% psoriatic JIA and none in the undifferentiated group. Some studies report up to 15% of the healthy population are low grade ANA positive. [1]
Patients diagnosed with systemic JIA had significantly raised C-reactive protein (CRP) levels with a median of 150 ug/dL (IQR 95-205) with 50% having both a raised CRP and Erythrocyte sedimentation rate (ESR) with a median ESR 98 mm/hr (IQR 51-145). Furthermore 21.4% had a positive anti-streptolysin O titer (ASOT), 28% had raised Alanine aminotransferase (ALT) and all had raised platelet counts which is in keeping with the published literature of laboratory parameters indicative that systemic JIA is an autoinflammatory syndrome.
For patients with Enthesitis related JIA, 53.8% tested positive for HLA-B27 antigen. Across the 7 subgroups the ASOT was positive in 12.7% of patients which is suggestive of a background burden of Streptococcal infection in some of our cohort.
79.4% of the study cohort had a normal BMI as defined by the WHO BMI Z score charts, with 9.1% of patients classified as underweight and 4.8% classified as obese. Polyarticular JIA, as the commonest subgroup in our cohort, was Rheumatoid factor negative predominant and systemic JIA demonstrated a significant inflammatory profile, with a significantly elevated CRP (P value 0.025) and elevated platelet counts, however not statistically significant. Nonspecific ASOT elevation was seen in 12.7% of patients, most commonly in the systemic JIA subgroup, followed by poly RF negative subgroup. ANA positivity was present in all subgroups, in varying percentages, except for the undifferentiated group where all patients tested had negative ANA. 9% of patients were underweight, 9% were overweight and 4.8% were obese. As nutrition is a critical determinant of immune responses, with both micro and macronutrient deficiency altering immunocompetence and increasing risk for infection, together with the knowledge that malnutrition is the most common cause of immunodeficiency worldwide, we need to consider the impact of malnutrition on the laboratory marker profile of patients due to immune modulation of nutrient deficiency. Conversely it is appreciated that overnutrition and obesity also contribute to an altered immunity. [2,3]
Raised ASOT marker profile of our patients is suggestive of an associated Streptococcal infection burden. Baseline normal ranges of ASOT need to be established so that we may interpret the results in the context of our population where positive ranges in otherwise healthy patients may be higher. Further studies are needed to elucidate the impact of immune activation and the resultant effect on the local reference ranges of baseline autoantibodies, namely rheumatoid factor (RF) and anti-nuclear antibodies (ANA). Baseline normal ranges of ASOT need to be established so that we may interpret the results in the context of our population where positive ranges in otherwise healthy patients may well be higher.
"Geen opsomming beskikbaar."
"Geen opsomming beskikbaar."
Description
Thesis (MMed)--Stellenbosch, 2020.
Keywords
Juvenile idiopathic arthritis, Pediatric rheumatology, Immune-mediated disorders, Rheumatoid factor, Rheumatoid arthritis in children, Immunofluorescence, UCTD