HLA-B27 and spondyloarthropathy: value for early diagnosis?

Reliability and reproducibility of antinuclear antibody testing in pediatric rheumatology practice

Antinuclear antibody (ANA) testing is common practice among health care practitioners when evaluating children and adolescents with non-specific symptoms including fatigue and aches and pains. When positive, ANA results often lead to referrals to pediatric rheumatologists as these antibodies may be key indicators for specific pediatric rheumatologic diagnoses. The reliability and reproducibility of ANA tests varies with assay techniques and validation and interpretation of results. In the following article, review of ANA testing in pediatrics is provided along with case examples that demonstrate the reliability and reproducibility of these results in specific scenarios common in the practice of pediatric rheumatology. Guidelines for more accurate utilization of ANA testing are presented with the aim to improve testing and interpretation by ordering clinicians.

Pediatric back pain-Diagnostic algorithm

BACKGROUND

Back pain in the pediatric population is common. History and a thorough physical examination and a systematic work-up approach are key components to guide the physician in evaluating the possible causes of pain and providing appropriate treatment.

OBJECTIVE

The main aim of this review was to develop an algorithmic approach to assist physicians in the assessment of pediatric back pain. A comprehensive review of prevalence, differential diagnoses and proper management of pediatric back pain are also presented.

MATERIAL AND METHODS

An extensive literature search was performed in PubMed to gather articles on the prevalence, risk factors, diagnostic tools, differential diagnoses and appropriate management of pediatric back pain.

RESULTS

Available literature revealed that pediatric back pain is a common complaint. Although most cases are non-specific and self-limiting, there is a wide differential that should be considered including inflammatory, neoplastic, infectious and mechanical causes. Sedentary lifestyle, obesity and vigorous physical activity have been shown to increase the likelihood of developing back pain. We proposed an algorithm to guide the physician's decision about the next step in the diagnostic process.

CONCLUSION

A well-defined strategy in the diagnostic process is needed in approaching children/adolescents with back pain. This would have the benefit of minimizing costs, unnecessary tests and child/family anxiety as well as increasing the likelihood of early diagnosis and proper treatment.

Improving turnaround times for HLA-B*27 and HLA-B*57:01 gene testing: a Barts Health NHS Trust quality improvement project

Among other tests, Barts Health NHS Trust clinical transplantation laboratory conducts two important gene-detection tests: human leucocyte antigen (HLA)-B*27 (‘B27’, associated with the diagnosis of ankylosing spondylitis) and HLA-B*57:01 (‘B57’, associated with prediction of abacavir hypersensitivity disorder). The turnaround time (TaT) from sample receipt to return of results is important to clinicians and their patients but was not monitored. Furthermore, we anticipated an imminent increase in demand from a forthcoming pathology service merger, together with long-term increases with the rise of personalised genetic medicine.

In this quality improvement project, we identified current TaT performance and sources of delay. Over three plan-do-study-act (PDSA) cycles, we tested three change ideas, two involving using IT to remove manual administrative steps and alert us to samples needing progressing; both were retained. The other change involved separating out the targeted tests; we judged this not worthwhile with current demand levels, although something to be re-examined when volumes increase. During the project, we reduced mean TaT from 3.8 to 3.3 days and increased the proportion within our 5-day target from 78% to 100%. These have been sustained (at 3.4 days and 97%) for the 3 months following our PDSA cycles and illustrate that reducing variation can be as impactful as reducing the mean.

We conducted this project during the COVID-19 disruption, which reduced demand substantially. We took advantage of this to allow staff to spend time on these improvement activities. Another interesting feature of the work is that during the project, we compared changes in performance on our targeted B27/B57 tests with that on another comparable test as a control, to consider the impact of the general increased attention (the Hawthorne effect). We found that performance on this control also increased comparably, but then fell away after our project finished, while it did not for B27/B57.

Rates of spondyloarthropathies vary with age and ethnicity in HLAB27 uveitis

BACKGROUND/AIMS

To determine associations between HLAB27-positive uveitis, ethnicity and seronegative spondyloarthropathies (SpAs) in a New Zealand population.

METHODS

Retrospective observational cohort study. Medical records of all subjects with uveitis at Auckland District Health Board from 2008 to 2018 were reviewed for HLAB27 status, age of presentation, ethnicity and SpA.

RESULTS

In 10 years, 2567 subjects with uveitis were seen and 492 (19.2%) were HLAB27-positive. Of the HLAB27-positive subjects, 301 were male (60.3%) and median age was 37.8 years (IQR 29.7-50.0). Ethnicities were Caucasian (n=298, 60.6%), Asian (n=111, 22.6%), Maori (n=41, 8.2%) and Pacific Islander (n=38, 7.7%). Uveitis classification was anterior (n=478, 97.2%), intermediate (n=40, 8.1%), panuveitis (n=9, 1.8%) and scleritis (n=2, 0.4%). Maori or Pacific Islander ethnicity was associated with intermediate or panuveitis (p=0.003). Ankylosing spondylitis occurred in 163 subjects (33.1%); 29 (17.8%) were Maori or Pacific Islander. Subjects were younger (OR 0.982, p=0.009) and male (OR 1.980, p=0.001). There was no association with ethnicity or uveitis classification. Psoriatic arthritis (PsA) occurred in 11 subjects (2.2%). Chronic anterior uveitis was more common with PsA (27.3% vs 7.1%, p=0.023). There was no association with gender or ethnicity. Inflammatory bowel disease occurred in 19 subjects (3.8%) and reactive arthritis occurred in 14 subjects (2.8%). None developed chronic anterior uveitis (p=0.246 and p=0.227, respectively). There was no association with age at presentation, gender, ethnicity or uveitis classification.

CONCLUSION

This cohort of New Zealand-based subjects with HLAB27-positive uveitis showed a difference in age and ethnicity in uveitis subtypes and SpAs.

The clinical utility of human leucocyte antigen B27 in axial spondyloarthritis

The association between HLA-B27 and AS was first established in the early 1970s. Since then, our understanding of this disease has changed, such that we now recognize AS to be the extreme of the clinical phenotype within a disease spectrum known as axial SpA (axSpA). Recent advances in therapeutic options have driven the need for earlier diagnosis and many screening strategies have been proposed to facilitate this. In parallel, our understanding of axSpA genetics, and especially the contribution of HLA-B27, has expanded. In this article we will present and discuss the evidence supporting the use of HLA-B27 in clinical practice. We will briefly summarize the evolution of the concept of axSpA, the prevalence of HLA-B27 and axSpA and the potential role of HLA-B27 in the aetiopathogenesis of axSpA and focus on the utility of HLA-B27 in everyday clinical practice.

Psoriatic Eye Manifestations

The relationship between the eye and psoriasis has been recognized for decades, but the precise eye manifestations in patients with psoriasis and psoriatic arthritis are only recently coming to light. Psoriatic eye findings may include conjunctivitis, dry eye, episcleritis, and uveitis, all of which may precede articular changes. Uveitis, seen in 7% to 25% of psoriatic arthritis patients, may be recognized by the presence of conjunctival injection, photophobia, pain, lid swelling, or otherwise unexplained visual changes. Early recognition is paramount because its natural course may lead to vision loss. Immunopathogenesis has shown evidence for T-helper cell (Th) type 1 (Th1) and Th17 involvement in the pathogenesis of uveitis according to the murine experimental autoimmune uveitis model. Corticosteroids are the primary treatment modality; however, increasing emphasis has been placed on immunomodulators and biologics for more intractable cases. Referral to an ophthalmologist is essential for definitive diagnosis and treatment.

Ankylosing Spondylitis and Axial Spondyloarthritis in Patients With Long-term Inflammatory Bowel Disease: Results From 20 Years of Follow-up in the IBSEN Study

BACKGROUND

Patients with inflammatory bowel disease [IBD] often suffer from rheumatic manifestations, including inflammatory back disorders. The prevalence of these disorders late in the course of IBD is poorly investigated. The aim of this study was to estimate the prevalence of inflammatory back disorders in patients with IBD 20 years after diagnosis, and to investigate possible associations with IBD severity, HLA-B27, and the NOD2 genotype.

METHODS

A population-based cohort [the IBSEN study] was followed prospectively for 20 years. Information covering IBD activity and rheumatic diseases was collected at the regular follow-ups. HLA-B27 and NOD2 were analysed as present or absent.

RESULTS

At 20 years, 599 members of the original cohort were alive, of whom 470 [78.5%] were investigated [314 ulcerative colitis and 156 Crohn's disease patients]. Ankylosing spondylitis was diagnosed in 21 patients [4.5%], axial spondyloarthritis was diagnosed in 36 patients [7.7%], and inflammatory back pain was diagnosed in 54 patients [11.5%]. Chronic back pain [back pain > 3 months] was present in 220 patients [46.8%]. HLA-B27 was associated with ankylosing spondylitis, axial spondyloarthritis, and inflammatory back pain, whereas no significant association was found for NOD2. A more chronic IBD course was associated with axial spondyloarthritis.

CONCLUSIONS

Our data revealed a high prevalence of ankylosing spondylitis, axial spondyloarthritis, and inflammatory back pain 20 years after the IBD diagnosis. HLA-B27 but not NOD-2 was a predisposing factor for the inflammatory back disorders in IBD patients. Axial spondyloarthritis was associated with a more chronic active IBD disease course.

Use of Rheumatology Laboratory Studies Among Primary Pediatricians

Rheumatology laboratory tests are often inappropriately ordered in situations for which they are of low diagnostic utility. We surveyed pediatricians to investigate reasons for ordering these tests. The response rate was 15.3% (93/609). The most commonly ordered tests were antinuclear antibody (ANA), anti-double-stranded DNA (dsDNA) antibody, and rheumatoid factor (RF). Of the 89% (83/93) who ordered an ANA, 86% ordered it for correct/possibly correct reasons; of the 73% (68/93) who ordered RF, 80% did so for correct/possibly correct reasons; and among the 59% (54/92) who had ordered anti-dsDNA antibody, 34% ordered it for correct reasons. A positive relationship was seen between years since residency completion and correct use of ANA. However, positive associations were not seen between measures of pediatric rheumatology experience and correct use of other tests. Interventions are needed to improve pediatricians' utilization of rheumatology tests.

Developing a Risk-scoring Model for Ankylosing Spondylitis Based on a Combination of HLA-B27, Single-nucleotide Polymorphism, and Copy Number Variant Markers

OBJECTIVE

To develop a genotype-based ankylosing spondylitis (AS) risk prediction model that is more sensitive and specific than HLA-B27 typing.

METHODS

To develop the AS genetic risk scoring (AS-GRS) model, 648 individuals (285 cases and 363 controls) were examined for 5 copy number variants (CNV), 7 single-nucleotide polymorphisms (SNP), and an HLA-B27 marker by TaqMan assays. The AS-GRS model was developed using logistic regression and validated with a larger independent set (576 cases and 680 controls).

RESULTS

Through logistic regression, we built the AS-GRS model consisting of 5 genetic components: HLA-B27, 3 CNV (1q32.2, 13q13.1, and 16p13.3), and 1 SNP (rs10865331). All significant associations of genetic factors in the model were replicated in the independent validation set. The discriminative ability of the AS-GRS model measured by the area under the curve was excellent: 0.976 (95% CI 0.96-0.99) in the model construction set and 0.951 (95% CI 0.94-0.96) in the validation set. The AS-GRS model showed higher specificity and accuracy than the HLA-B27-only model when the sensitivity was set to over 94%. When we categorized the individuals into quartiles based on the AS-GRS scores, OR of the 4 groups (low, intermediate-1, intermediate-2, and high risk) showed an increasing trend with the AS-GRS scores (r² = 0.950) and the highest risk group showed a 494× higher risk of AS than the lowest risk group (95% CI 237.3-1029.1).

CONCLUSION

Our AS-GRS could be used to identify individuals at high risk for AS before major symptoms appear, which may improve the prognosis for them through early treatment.

Is HLA-B27 Increased in Patients Diagnosed with Undifferentiated Arthritis? Results from the Leiden Early Arthritis Cohort

Objective.

Undifferentiated arthritis (UA) is a common form of arthritis. According to the Assessment of Spondyloarthritis international Society (ASAS) criteria for peripheral spondyloarthritis (pSpA), HLA-B27 can be used to help classify patients with pSpA. We tested whether HLA-B27 is increased in patients diagnosed with UA.

Methods.

Prevalence of HLA-B27 was compared between healthy controls and patients with UA. SpA features were compared between HLA-B27-positive and -negative UA, and SpA.

Results.

We found 10.1% of UA (38/375) versus 7.2% (403/5584) of controls were HLA-B27-positive (OR 1.5, 95% CI 1.0–2.1; p = 0.037). HLA-B27-positive patients with UA had more SpA features than HLA-B27-negative patients (mean 1.6, SD 1.0, and 0.9 SD 0.6; p < 0.001), but patients with SpA had significantly more SpA features (mean 4.5, SD 1.5; p < 0.001). Family history and preceding infection were features more common in HLA-B27-positive than in HLA-B27-negative UA (15.8% vs 1.3%, p = 0.04 and 15.8% vs 2.6%, p = 0.04). After HLA-B27 testing, 21 additional patients (5.6%) with UA could potentially have been classified with pSpA according to the ASAS criteria.

Conclusion.

HLA-B27 is more common in patients with UA than in controls. However, the yield of HLA-B27 testing in UA is low. Our results suggest that HLA-B27 testing should be reserved for patients with additional SpA features.

Testing for Rheumatological Diagnoses in Children

Paediatricians often order laboratory and radiological tests to identify children with potential rheumatological disease prior to subspeciality referral. However, the pattern of testing suggests inadequate understanding of their diagnostic utility and limitations. Herein we will address some of the most common rheumatological diagnoses encountered in the subspeciality clinic - juvenile idiopathic arthritis (JIA), juvenile spondyloarthritis (JSpA) and systemic lupus erythematosus (SLE), and related connective tissue diseases - and the tests most frequently ordered to diagnose them: anti-nuclear antibodies (ANA), rheumatoid factor (RF), human leukocyte antigen (HLA)-B27 and radiological tests. This article will highlight the sensitivity, specificity and positive predictive value of the tests. In general, none of these tests were appropriate to use as rheumatological 'screens', as no individual test was diagnostic. Specific tests should be ordered only when there is a high clinical index of suspicion for a particular disease entity. Greater understanding of a test's diagnostic utility should decrease unnecessary testing, anxiety and expense and aid in interpretation.

Patients with juvenile psoriatic arthritis comprise two distinct populations

OBJECTIVE

Psoriatic arthritis (PsA) in children is clinically heterogeneous. We examined a large population of children with juvenile PsA for evidence of phenotypic clustering that could suggest the presence of distinct clinical entities.

METHODS

We reviewed the medical records of 139 patients meeting the Vancouver criteria for juvenile PsA. To identify segregation into phenotypic groups, we compared younger patients with their older counterparts and subjected the whole population to 2-step cluster analysis.

RESULTS

Among patients with juvenile PsA, the age at onset is biphasic, with peaks occurring at approximately 2 years of age and again in late childhood. Compared with children ages 5 years and older, younger patients are more likely to be female, exhibit dactylitis and small joint involvement, and express antinuclear antibodies. Progression to polyarticular disease (>or=5 joints) is more common in younger children, although joint involvement remains oligoarticular in the majority of children. In contrast, older patents tend to manifest enthesitis, axial joint disease, and persistent oligoarthritis. Uveitis is equally represented in both age groups. Despite a higher utilization of methotrexate therapy, younger patients required, on average, more than twice as long to achieve clinical remission (23 months versus 9.2 months; P = 0.044). Cluster analysis identified largely overlapping subgroups but suggested that the presence of dactylitis, rather than age, has the greatest capacity to predict essential features of the clinical phenotype.

CONCLUSION

Juvenile PsA comprises 2 distinct populations of patients. Although the pathophysiologic correlate of this finding remains undefined, future studies should avoid the assumption that PsA in childhood constitutes a single etiologic entity.

How to diagnose axial spondyloarthritis early

BACKGROUND

Chronic low back pain (LBP), the leading symptom of ankylosing spondylitis (AS) and undifferentiated axial spondyloarthritis (SpA), precedes the development of radiographic sacroiliitis, sometimes by many years.

OBJECTIVE

To assign disease probabilities and to develop an algorithm to help in the early diagnosis of axial SpA.

METHODS

Axial SpA comprises AS and undifferentiated SpA with predominant axial involvement. Clinical features include inflammatory back pain (IBP), alternating buttock pain, enthesitis, arthritis, dactylitis, acute anterior uveitis, a positive family history, psoriasis, inflammatory bowel disease, and good response to NSAIDs. Associated laboratory findings include raised acute phase reactions, HLA-B27 association, and abnormalities on skeletal imaging. Sensitivities, specificities, and likelihood ratios (LRs) of these parameters were determined from published studies. A 5% prevalence of axial SpA among patients with chronic LBP was used. The probability of the presence of axial SpA, depending on the presence or absence of the above clinical features of SpA, was determined. A probability of > or = 90% was used to make a diagnosis of axial SpA.

RESULTS

The presence of inflammatory back pain features increased the probability of axial SpA from the background 5% prevalence to 14%. The presence of 2-3 SpA features was necessary to increase the probability of axial SpA to 90%. The highest LRs were obtained for HLA-B27 and MRI. Diagnostic algorithms to be used in daily practice were suggested.

CONCLUSIONS

This approach can help clinicians to diagnose with a high degree of confidence axial SpA at an early stage in patients with IBP who lack radiographic sacroiliitis.

How to diagnose axial spondyloarthritis early

BACKGROUND

Chronic low back pain (LBP), the leading symptom of ankylosing spondylitis (AS) and undifferentiated axial spondyloarthritis (SpA), precedes the development of radiographic sacroiliitis, sometimes by many years.

OBJECTIVE

To assign disease probabilities and to develop an algorithm to help in the early diagnosis of axial SpA.

METHODS

Axial SpA comprises AS and undifferentiated SpA with predominant axial involvement. Clinical features include inflammatory back pain (IBP), alternating buttock pain, enthesitis, arthritis, dactylitis, acute anterior uveitis, a positive family history, psoriasis, inflammatory bowel disease, and good response to NSAIDs. Associated laboratory findings include raised acute phase reactions, HLA-B27 association, and abnormalities on skeletal imaging. Sensitivities, specificities, and likelihood ratios (LRs) of these parameters were determined from published studies. A 5% prevalence of axial SpA among patients with chronic LBP was used. The probability of the presence of axial SpA, depending on the presence or absence of the above clinical features of SpA, was determined. A probability of > or = 90% was used to make a diagnosis of axial SpA.

RESULTS

The presence of inflammatory back pain features increased the probability of axial SpA from the background 5% prevalence to 14%. The presence of 2-3 SpA features was necessary to increase the probability of axial SpA to 90%. The highest LRs were obtained for HLA-B27 and MRI. Diagnostic algorithms to be used in daily practice were suggested.

CONCLUSIONS

This approach can help clinicians to diagnose with a high degree of confidence axial SpA at an early stage in patients with IBP who lack radiographic sacroiliitis.

A prospective study of early diagnostic investigations in the diagnosis of ankylosing spondylitis

This study was designed to assess the relative values current of locally available investigations in the early diagnosis of inflammatory sacroiliitis. Consecutive patients attending routine rheumatology clinics in Aberdeen clinically considered by consultant rheumatologists to have inflammatory back disease but with insufficient criteria to firmly establish a diagnosis of ankylosing spondylitis were included. Patients were assessed using a standard questionnaire, clinical examination of spinal movements, plain radiology of the sacroiliac joints, computerised tomographic scanning of the sacroiliac joints and HLA-B27 typing. Patients were systematically followed up using repeated clinical and radiological examination for five years. Plain film evidence of grade 2 radiological sacroiliitis (bilateral or unilateral) was found to be the most reliable predictor for the development of ankylosing spondylitis satisfying the New York criteria at 5 year follow up. CT scanning and HLA-B27 typing were of no added value in this series and the clinical questionnaire lacked specificity. It is concluded that the combination of clinical history, examination and plain film radiology are currently reliable criteria for diagnosing the subsequent development of ankylosing spondylitis satisfying established criteria.

Interleukin 1 gene cluster polymorphisms in multiplex families with spondylarthropathies

Interleukin 1alpha (IL-1alpha) has been implicated in the pathogenesis of infectious, auto-immune and inflammatory diseases. Polymorphisms in the genes encoding IL-1alpha, IL-1beta and the IL-1 receptor antagonist (ILRN) molecules have been associated with several inflammatory diseases. As the marker D2S160 has been characterized as a candidate locus for Ankylosing Spondylitis (AS) after a genome-wide scan, and since this locus is located approximately 0.3 cM telomeric to the IL-1 gene cluster, we hypothesized that these cytokines might be good candidates for Spondylarthropathies (SpA). Therefore we tested this hypothesis using the transmission disequilibrium test (TDT) in 37 families representing 217 subjects from three intragenic IL-1 gene cluster polymorphisms, the IL1B Taq I, the ILRN 2nd intron, and the IL1A Nco I, taking HLA B27 status into account or not. In conclusion, by means of intra-familial TDT analysis we found no linkage or intra-familial association between SpA and the three IL-1 gene-cluster polymorphisms in SpA multiplex family material.

HLA-B27 expression by flow cytometry: an analysis of 7 years quality assurance data

The Royal College of Pathologists of Australasia Quality Assurance Programs Pty. Ltd. has been monitoring HLA-B27 assignment by flow cytometry for 7 years as part of the Immunology Program. Here we present data that demonstrates a gradual improvement in reports of false positive and negative results. Many participating laboratories demonstrate an ability to assign HLA-B27 status correctly by flow cytometric means. This ability appears to be independent of reagent and methodology. However a small number of laboratories produce consistently unacceptable results that suggest poor quality assurance practice.

Studying patients with inflammatory back pain and arthritis of the lower limbs clinically and by magnetic resonance imaging: many, but not all patients with sacroiliitis have spondyloarthropathy

OBJECTIVE

Clinical and magnetic resonance imaging (MRI) data of 170 consecutive patients with inflammatory back pain (IBP) and/or oligoarthritis of the lower limbs were evaluated in a retrospective study. The aim was to determine the frequency of sacroiliitis and spondyloarthropathy (SpA) in this population, and to assess the significance of HLA B27 measurements for diagnosis in early disease.

METHODS

Pelvic X-rays were performed in all IBP patients and dynamic MRI of the sacroiliac joints in patients with IBP who had indefinite results on sacroiliac X-rays (n = 32).

RESULTS

European Spondyloarthropathy Study Group criteria for SpA were fulfilled by 106/170 patients (62.4%); eight additional patients had symptoms suggestive of SpA (4.7%). The most frequent SpA subset was undifferentiated SpA (uSpA), diagnosed in 46/106 patients (43.4%). Sacroiliitis was detected by MRI in 21/32 patients with IBP and unclear X-rays (65.6%). Of those, 14 were diagnosed as SpA and seven females with moderate unilateral sacroiliitis, but no features of SpA, also not on follow-up (at least 1 yr), were classified as undifferentiated sacroiliitis (US). Ten of the 14 SpA (71.4%) and none of the seven US patients were HLA B27 positive.

CONCLUSION

HLA B27 positivity in IBP patients with MRI-proven sacroiliitis positively predicts SpA. uSpA is a frequent SpA subset. There are HLA B27-negative non-SpA patients with moderate unilateral sacroiliitis whom we propose to be classified as US.

Spondyloarthritides in females

Few studies have been performed regarding clinical, radiological and prognostic features of females with spondyloarthropathies other than ankylosing spondylitis (AS). In AS, clinical manifestations appear similar in men and women, whereas radiological features appear more frequent and severe in males. However, no consistent differences in outcome and mortality between men and women have been disclosed. Although fetal outcome is not compromised in women with spondyloarthropathy (SpA), the interaction of pregnancy and SpA has been studied in detail only in AS. Spinal disease is unchanged while peripheral arthritis and uveitis are suppressed during childbearing. Due to possible maternal and fetal side-effects, NSAIDs must be discontinued during the last 8 weeks of pregnancy, but during lactation several NSAIDs can be used. Treatment with sulphasalazine is compatible with pregnancy and lactation. Children of AS patients exhibit a slightly increased risk of developing SpA later in life.

HLA-B*27 typing by group-specific hybridization in microtiter plates

We have developed and evaluated a test for HLA-B*27 based on PCR and DNA hybridization in microtiter plates. A region within exon 2 of the HLA-B gene is amplified and labeled by PCR and the amplification product is hybridized to a group-specific HLA-B*27 and a generic control oligonucleotide probe in two separate cavities of the plate. Bound sequences are detected using an ELISA-like protocol. The assay has been evaluated on 254 DNA samples routinely received for B27 testing in parallel with serological and SSP-PCR typing. Results were concordant in typing 102 HLA-B27-positive and 152 HLA-B27-negative individuals except for two samples containing HLA-B*73, which stained B27 positive in the microwell test. The new procedure is rapid and simple to perform, and the microwell format is particularly suitable for automation.

An integrated multiplex-PCR and PCR-RFLP typing system for markers associated with seronegative arthritides

The system was designed with emphasis on the identification HLA-B alleles and genotypes associated or potentially associated with seronegative arthritides. By using a combination of multiplex SSP and PCR-RFLPs, the assays can be economically performed on a large range of sample sizes in diagnosis and epidemiology. 24 HLA-B alleles and subtypes can be discriminated, including options for PCR-RFLP or sequence specific amplification of the allele groups B27 and B60 (B*4001 and B*4007). In addition, the internal control carries central MHC polymorphisms, which can help to identify HLA extended halplotypes. False negatives, caused by preferential amplification of the internal control under suboptimal PCR conditions, were prevented by employing new, optimized PCR buffer. Four of the HLA-B primers were pooled into a multiplex reaction whose products were subtyped by digestion with seven restriction endonucleases. Specificity and sensitivity were verified in a panel of 68 homozygous cell lines and 200 heterozygous samples. An HLA-B*27-B*40 hybrid allele was observed in 3 out of 95 B*27-positive individuals from Berlin, Germany. Such an allele could be mistyped by some published assays as a B*27/B*40 heterozygote, a genotype reported to confer an increased risk for ankylosing spondylitis.

Prevalence of spondylarthropathies in HLA-B27 positive and negative blood donors

OBJECTIVE

To determine the overall prevalence of spondylarthropathy (SpA) among whites.

METHODS

To screen for SpA symptoms, such as inflammatory back pain (IBP), joint swelling, psoriasis, and uveitis, or a specific family history, questionnaires were mailed to 348 blood donors (174 HLA-B27 positive and 174 HLA-B27 negative). From the responding 273 persons (78%; 140 B27 positive, 133 B27 negative), 126 were selected for further evaluation based on the symptoms reported. Of this group, 90 persons agreed to undergo physical examination (71.4%; 46 B27 positive, 44 B27 negative). There was no difference between the B27-positive and -negative groups in terms of age (mean +/- SD 38.4 +/- 10 versus 39.5 +/- 11 years) and sex ratio (67% versus 68% were men). In addition, 58 donors (32 B27 positive, 26 B27 negative) agreed to undergo magnetic resonance imaging (MRI) of the sacroiliac joints. A diagnosis of SpA and ankylosing spondylitis (AS) was made according to the European Spondylarthropathy Study Group criteria and the New York criteria.

RESULTS

SpA was diagnosed in 20 persons: 19 of 140 B27-positive (13.6%) and 1 of 133 B27-negative (0.7%) subjects (15 male and 5 female). AS was diagnosed in 9 persons (7 male and 2 female; 45%), undifferentiated SpA (USpA) in 7 (5 male and 2 female; 35%), psoriatic arthritis (PsA) in 3 (2 male and 1 female; 15%), and chronic reactive arthritis (ReA; Reiter's syndrome) in 1 (male; 5%). On the basis of a B27 frequency of 9.3% among the population of Berlin (3.47 million persons), the estimated prevalence of SpA was 1.9%, AS was 0.86%, USpA was 0.67%, and PsA was 0.29%. The relative risk of developing SpA in B27-positive subjects was calculated as 20.7 (95% confidence interval 4.6-94.2; P = 0.001). Of 58 persons with IBP, sacroiliitis was detected by MRI in 15 of 32 B27-positive (46.9%) and 1 of 26 B27-negative (3.9%) subjects (P = 0.002). Four of these 16 donors did not fulfill diagnostic criteria for SpA.

CONCLUSION

With a calculated prevalence of 1.9%, spondylarthropathies are among the most frequent rheumatic diseases in the white population. HLA-B27 positive persons carry a 20-fold increased risk of developing SpA. AS and USpA are the most frequent SpA subtypes. Persons with IBP who are B27 positive have a 50% likelihood of having sacroiliitis.