Intra- and interlaboratory reproducibility evaluation toward international validation status of the AmpFire assay.

To meet the screening goal of WHO's 90-70-90 strategy aimed at eliminating cervical cancer (CC) by 2030, clinical validation of human papillomavirus (HPV) assays is essential to provide accurate and valid results through fulfilling three criteria of the international validation guidelines (IVGs). Previously, the clinical accuracy of the AmpFire® HPV Screening 16/18/HR assay (AmpFire assay) was reported but reproducibility data are lacking. Here, we aim to evaluate the intra- and inter-laboratory reproducibility of the AmpFire assay. The reproducibility of the isothermal AmpFire assay was assessed using 556 cervical cell samples collected from women attending CC screening and biobanked in a Belgian HPV national reference center. This assay detects HPV16, HPV18, and 12 other high-risk HPV (hrHPV) types (31/33/35/39/45/51/52/56/58/59/66/68) in aggregate. Lower 95% confidence interval bound around the assay's reproducibility should exceed 87%, with κ ≥ 0.50. Additionally, a literature review of the assay's clinical performance was performed. The AmpFire assay showed an excellent intralaboratory (96.4%, 95% CI:94.5-97.8%, κ = 0.920) and interlaboratory (95.3%, 95% CI:93.2-96.9%, κ = 0.897) reproducibility. One study demonstrated noninferior sensitivity of a prototype AmpFire assay targeting 15 hrHPV types (including HPV53) to detect CIN2+. However, clinical specificity became similar to the comparator after removing HPV53 from analyses. The low-cost and easy-to-use AmpFire assay presents excellent reproducibility and-after removing HPV53 from the targeted types-fulfills also clinical accuracy requirements. Inclusion of HPV53, which is not recognized as carcinogenic, comprises clinical specificity of screening assays.

The Sansure® Human Papillomavirus DNA Diagnostic Kit offers excellent reproducibility performance for the detection of high-risk HPV.

Cervical cancer screening is a cornerstone of cervical cancer elimination. Detection of high-risk human papillomavirus (hrHPV) is recommended as the first step in screening provided that the assay used has been adequately validated. The Sansure® Human Papillomavirus DNA Diagnostic Kit is a new assay designed to detect HPV16, HPV18 and 13 other HPV in aggregate. The study aimed to evaluate the intra- and interlaboratory reproducibility of the assay according to international guidelines. Five hundred and fifty cervical residual cell samples from women attending cervical cancer screening were selected from the biobank of the HPV National Reference Centre in Belgium and used in this study. After DNA extraction, HPV was tested using the Sansure® Human Papillomavirus DNA Diagnostic Kit. The lower 95% confidence limit around the general reproducibility of this assay should be greater than or equal to 87%, with κ ≥ 0.50. Five hundred and thirty-three samples had valid results. The Sansure® Human Papillomavirus DNA Diagnostic Kit demonstrated an excellent intra-laboratory reproducibility of 93.8% (95% confidence interval [CI]: 91.4-95.7, κ = 0.85). The interlaboratory reproducibility was 93.4 (95% CI: 91.0-95.4, κ = 0.84). Intra and interlaboratory reproducibility were also excellent at the genotype level. Excluding HPV53 single infection samples from the analyses also resulted in excellent agreement. These data show that the Sansure® Human Papillomavirus DNA Diagnostic Kit is highly reproducible.

Evaluation of the clinical performance of OncoPredict HPV® SCR assay within the VALGENT-2 framework.

Human papillomavirus (HPV) assays used in cervical cancer screening should be clinically validated according to international criteria. OncoPredict HPV® Screening (SCR) is a partial genotyping multiplex real-time PCR assay targeting E6/E7 genes of 13 high-risk (hr) HPVs. OncoPredict HPV® SCR (index assay) identifies HPV-16 and HPV-18 separately, 11 other hrHPV in aggregate and includes quality controls for sample adequacy, DNA extraction efficiency and PCR inhibition. 1300 VALGENT-2 study samples (from women aged 20-60 attending the Scottish cervical cancer screening program) were tested with the index assay and the GP5+/6+ PCR enzyme immunoassay (standard comparator assay). Non-inferior accuracy detecting cervical intraepithelial neoplasia of grade 2 or worse (CIN2+) of the index versus comparator was verified. Intra- and interlaboratory reproducibility of the index was evaluated by overall concordance and Cohen's kappa, using a sub-population (n = 526). Relative sensitivity and specificity for CIN2+ of the index versus comparator were 1.01 (95% confidence interval [CI]: 0.99-1.03) and 1.02 (95% CI: 1.0-1.04), respectively. Noninferiority p values were all ≤0.05, except for CIN3+ in patients ≥30 years. Excellent intra- and interlaboratory reproducibility was shown with concordance >98% and kappas >0.95. OncoPredict HPV® SCR fulfills the three international validation criteria for hrHPV DNA tests in cervical cancer screening.

Intra- and interlaboratory reproducibility of the RIATOL qPCR HPV genotyping assay.

The implementation of cervical screening based on human papillomavirus (HPV) continues to progress rapidly across countries. Evidence has shown that assays detecting high-risk human papillomavirus (hrHPV) deoxyribonucleic acid (DNA) are more effective than cytology-based screening. Validation of new hrHPV DNA assays requires both noninferior clinical accuracy compared to a standard comparator for cervical precancer and good reproducibility. This study builds upon previous diagnostic accuracy assessments of the RIATOL HPV genotyping qPCR assay and aims to evaluate the international validation criteria for reproducibility. The intra- and interreproducibility of the RIATOL-qPCR assay were assessed using 550 remnant cervical cell material from the cytology archive of the National Reference Center for HPV in Belgium. Specimens were collected in the context of cervical cancer screening and tested in two different laboratories. The international reproducibility criteria include the lower bound of 95% confidence interval of the intra- and interlaboratory agreement regarding the detection of hrHPV DNA exceeding 87% with kappa ≥0.50. The RIATOL-qPCR assay demonstrated excellent intralaboratory reproducibility, achieving an overall agreement of 98.2 (95% CI 96.6-99.1%) and a kappa of 0.96. Interlaboratory testing showed an overall agreement of 98.5 (95% CI 97.1-99.4%) with a kappa of 0.97. The RIATOL-qPCR assay fulfills the third criterion for HPV test reproducibility requirement for use in cervical cancer screening.

COVID-19 vaccine effectiveness against symptomatic infection and hospitalisation in Belgium, July 2021 to May 2022.

BackgroundThe Belgian COVID-19 vaccination campaign aimed to reduce disease spread and severity.AimWe estimated SARS-CoV-2 variant-specific vaccine effectiveness against symptomatic infection (VEi) and hospitalisation (VEh), given time since vaccination and prior infection.MethodsNationwide healthcare records from July 2021 to May 2022 on testing and vaccination were combined with a clinical hospital survey. We used a test-negative design and proportional hazard regression to estimate VEi and VEh, controlling for prior infection, time since vaccination, age, sex, residence and calendar week of sampling.ResultsWe included 1,932,546 symptomatic individuals, of whom 734,115 tested positive. VEi against Delta waned from an initial estimate of 80% (95% confidence interval (CI): 80-81) to 55% (95% CI: 54-55) 100-150 days after the primary vaccination course. Booster vaccination increased initial VEi to 85% (95% CI: 84-85). Against Omicron, an initial VEi of 33% (95% CI: 30-36) waned to 17% (95% CI: 15-18), while booster vaccination increased VEi to 50% (95% CI: 49-50), which waned to 20% (95% CI: 19-21) 100-150 days after vaccination. Initial VEh for booster vaccination decreased from 96% (95% CI: 95-96) against Delta to 87% (95% CI: 86-89) against Omicron. VEh against Omicron waned to 73% (95% CI: 71-75) 100-150 days after booster vaccination. While recent prior infections conferred higher protection, infections occurring before 2021 remained associated with significant risk reduction against symptomatic infection. Vaccination and prior infection outperformed vaccination or prior infection only.ConclusionWe report waning and a significant decrease in VEi and VEh from Delta to Omicron-dominant periods. Booster vaccination and prior infection attenuated these effects.

DNA copy number concentration measured by digital and droplet digital quantitative PCR using certified reference materials.

The value assignment for properties of six certified reference materials (ERM-AD623a-f), each containing a plasmid DNA solution ranging from 1 million to 10 copies per µL, by using digital PCR (dPCR) with the BioMark™ HD System (Fluidigm) has been verified by applying droplet digital PCR (ddPCR) using the QX100 system (Bio-Rad). One of the critical factors in the measurement of copy number concentrations by digital PCR is the partition volume. Therefore, we determined the average droplet volume by optical microscopy, revealing an average droplet volume that is 8 % smaller than the droplet volume used as the defined parameter in the QuantaSoft software version 1.3.2.0 (Bio-Rad) to calculate the copy number concentration. This observation explains why copy number concentrations estimated with ddPCR and using an average droplet volume predefined in the QuantaSoft software were systematically lower than those measured by dPCR, creating a significant bias between the values obtained by these two techniques. The difference was not significant anymore when the measured droplet volume of 0.834 nL was used to estimate copy number concentrations. A new version of QuantaSoft software (version 1.6.6.0320), which has since been released with Bio-Rad's new QX200 systems and QX100 upgrades, uses a droplet volume of 0.85 nL as a defined parameter to calculate copy number concentration.

Evaluation of the Allplex HPV assay's adherence to international guidelines for cervical cancer screening in clinician-collected samples.

Clinically validated human papillomavirus (HPV) assays are crucial in cervical cancer screening. In this study, we evaluated the Allplex HPV HR Detection assay (Seegene, SouthKorea) for its clinical accuracy and reproducibility according to the international criteria, using the RealTime High Risk HPV m2000 assay (Abbott, USA) as standard comparator. The Allplex HPV HR assay exhibits significant non-inferior sensitivity to detect cervical intraepithelial neoplasia grade (CIN) 2 or worse (CIN2+) with a ratio of 1.00 (95% CI: 0.97-1.03, P = 0.006), insignificant non-inferior sensitivity to detect CIN3+ with a ratio of 1.00 (95% CI: 0.88-1.13, P = 0.098), and non-inferior specificity to exclude CIN2+ with a ratio of 0.99 (95% CI: 0.99-1.00, P < 0.001) compared to the standard comparator. In addition, the assay shows an excellent reproducibility within the same laboratory [96.5% (95% CI: 94.6-97.9) with a kappa value of 0.91 (95% CI: 0.87-0.95)] and between laboratories [96.7% (95% CI: 94.8-98.0) with a kappa value of 0.91 (95% CI: 0.87-0.95)] for overall high-risk HPV positivity as well as for each individual HPV type. Pooling our study data with those of another independent study supports the consistency of our findings. We conclude that both the clinical accuracy to detect cervical precancer and the reproducibility of Allplex HPV HR Detection assay fulfill the international validation criteria of use in cervical cancer screening.IMPORTANCEThe clinical validation of human papillomavirus (HPV) assays in accordance with well-established international guidelines is crucial to ensure that only validated assays are used in the context of screening (Meijer et al., Int J Cancer, 2009). The guidelines, developed by an international consortium, require that a novel HPV assay has non-inferior accuracy against a standard comparator test for the detection of cervical intraepithelial neoplasia grade (CIN) 2 or worse (CIN2+). Additionally, a new HPV assay should meet specific criteria for both intra- and inter-laboratory reproducibility to ensure the assay consistently exhibits technical precision and robust performance. Pooling our study data with those of another independent study supports the consistency of our findings. In conclusion, both the clinical accuracy to detect cervical precancer and the reproducibility of Allplex HPV HR Detection assay fulfill the international validation criteria of use in cervical cancer screening.

Assessment of the clinical and analytical performance of three Seegene Allplex SARS-CoV-2 assays within the VALCOR framework.

The coronavirus disease 2019 (COVID-19) pandemic demonstrated the need for accurate diagnostic testing for the early detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Although the pandemic has ended, accurate assays are still needed to monitor viral spread at national levels and beyond through population and wastewater surveillance. To enhance early detection, SARS-CoV-2 assays should have high diagnostic accuracy and should be validated to assure accurate results. Three distinct SARS-CoV-2 assays were evaluated with clinical samples using the VALCOR (VALidation of SARS-CORona Virus-2 assays) framework, with the TaqPath COVID-19 assay (ThermoFisher Scientific, USA) as a comparator. We evaluated clinical sensitivity, specificity, limit of detection (LOD), and overall concordance between comparator and three index Allplex SARS-CoV-2 assays (Seegene, South Korea): Allplex-SC2, Allplex-SC2Fast (Fast PCR), and Allplex-SC2FabR (SARS-CoV-2/FluA/FluB/respiratory syncytial virus). Analytical performance and LOD of index assays were assessed using a dilution series of three synthetic SARS-CoV-2 sequence reference materials (RMs). Ninety SARS-CoV-2 positives and 90 SARS-CoV-2 negatives were tested. All Allplex assays had 100.0% sensitivity (95%CI = 95.9%-100.0%). Allplex-SC2 and Allplex-SC2Fast assays had 97.8% specificity (95%CI = 92.3%-99.7%) and 98.9% overall concordance [κ = 0.978 (95%CI = 0.947-1.000)]. Allplex-SC2FabR assay showed 100.0% specificity (95%CI = 95.9%-100.0%) and 100.0% overall concordance [κ = 1.000 (95%CI = 1.000-1.000)]. LOD assessment of index assays revealed detection down to 2.61 × 102 copies/mL in clinical samples, while the analytical LOD was 9.00 × 102 copies/mL. In conclusion, the evaluation of the three Seegene Allplex SARS-CoV-2 assays showed high sensitivity and specificity and an overall good assay concordance with the comparator. The assays showed low analytical LOD using RM and even a slightly lower LOD in clinical samples. Non-overlapping target gene sequences between SARS-CoV-2 assays and RMs emphasize the need for aligning targeted sequences of diagnostic assays and RMs.IMPORTANCEThe coronavirus disease 2019 pandemic has a significant impact on global public health, economies, and societies. As shown through the first phases of the pandemic, accurate and timely diagnosis is crucial for disease control, prevention, and monitoring. Though the pandemic phase of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has concluded, diagnostic assays remain in demand to monitor SARS-CoV-2 at the individual patient level, regionally, and nationally, as well as to remain an infectious disease preparedness instrument to monitor any new SARS-CoV-2 dissemination across borders using population and wastewater surveillance. The anticipation by WHO and central health care policy entities such as the Center for Disease Control, EMA, and multiple national health authorities is that SARS-CoV-2 will reside as an endemic respiratory disease for years to come. The key strategic consideration is hence shifting from combating a pandemic situation with a high number of patients to instead allowing precise diagnostics of suspected patients with the intention of correct management in a low-prevalence setting.

Association between COVID-19 Primary Vaccination and Severe Disease Caused by SARS-CoV-2 Delta Variant among Hospitalized Patients: A Belgian Retrospective Cohort Study.

We aimed to investigate vaccine effectiveness against progression to severe COVID-19 (acute respiratory distress syndrome (ARDS), intensive care unit (ICU) admission and/or death) and in-hospital death in a cohort of hospitalized COVID-19 patients. Mixed effects logistic regression analyses were performed to estimate the association between receiving a primary COVID-19 vaccination schedule and severe outcomes after adjusting for patient, hospital, and vaccination characteristics. Additionally, the effects of the vaccine brands including mRNA vaccines mRNA-1273 and BNT162b2, and adenovirus-vector vaccines ChAdOx1 (AZ) and Ad26.COV2.S (J&J) were compared to each other. This retrospective, multicenter cohort study included 2493 COVID-19 patients hospitalized across 73 acute care hospitals in Belgium during the time period 15 August 2021-14 November 2021 when the Delta variant (B1.617.2) was predominant. Hospitalized COVID-19 patients that received a primary vaccination schedule had lower odds of progressing to severe disease (OR (95% CI); 0.48 (0.38; 0.60)) and in-hospital death (OR (95% CI); 0.49 (0.36; 0.65)) than unvaccinated patients. Among the vaccinated patients older than 75 years, mRNA vaccines and AZ seemed to confer similar protection, while one dose of J&J showed lower protection in this age category. In conclusion, a primary vaccination schedule protects against worsening of COVID-19 to severe outcomes among hospitalized patients.

Clinical Severity of SARS-CoV-2 Omicron Variant Compared with Delta among Hospitalized COVID-19 Patients in Belgium during Autumn and Winter Season 2021-2022.

This retrospective multi-center matched cohort study assessed the risk for severe COVID-19 (combination of severity indicators), intensive care unit (ICU) admission, and in-hospital mortality in hospitalized patients when infected with the Omicron variant compared to when infected with the Delta variant. The study is based on a causal framework using individually-linked data from national COVID-19 registries. The study population consisted of 954 COVID-19 patients (of which, 445 were infected with Omicron) above 18 years old admitted to a Belgian hospital during the autumn and winter season 2021-2022, and with available viral genomic data. Patients were matched based on the hospital, whereas other possible confounders (demographics, comorbidities, vaccination status, socio-economic status, and ICU occupancy) were adjusted for by using a multivariable logistic regression analysis. The estimated standardized risk for severe COVID-19 and ICU admission in hospitalized patients was significantly lower (RR = 0.63; 95% CI (0.30; 0.97) and RR = 0.56; 95% CI (0.14; 0.99), respectively) when infected with the Omicron variant, whereas in-hospital mortality was not significantly different according to the SARS-CoV-2 variant (RR = 0.78, 95% CI (0.28-1.29)). This study demonstrates the added value of integrated genomic and clinical surveillance to recognize the multifactorial nature of COVID-19 pathogenesis.

Indications for a genetic association of a VCP polymorphism with the pathogenesis of sporadic Paget's disease of bone, but not for TNFSF11 (RANKL) and IL-6 polymorphisms.

Paget's disease of bone (PDB) is, after osteoporosis, the second most common metabolic bone disorder in the elderly Caucasian population. Mutations in the sequestosome 1 gene (SQSTM1) are responsible for the etiology of PDB in a subset of patients, but the disease pathogenesis in the remaining PDB patients is still unknown. Therefore association studies investigating the relationship between genetic polymorphisms and sporadic PDB have been performed in order to find the susceptibility polymorphisms. In this paper, we sought to determine whether polymorphisms in 3 functional candidate genes play a role in the development of sporadic PDB: TNFSF11 (receptor activator of nuclear factor κB ligand, RANKL), VCP (valosin-containing protein) and IL-6 (interleukin 6). Analyzing 9 tag SNPs and 2 multi-marker tests (MMTs) in TNFSF11, 3 tag SNPs and 1 MMT in VCP and 8 tag SNPs in IL-6 in a population of 196 Belgian patients with sporadic PDB and 212 Belgian control individuals revealed that one VCP SNP (rs565070) turned out to be associated with PDB in this Belgian study population (p=5.5×10(-3)). None of the tag SNPs or MMTs selected for TNFSF11 or IL-6 was associated with PDB. Still, replication of our findings in the VCP gene in other populations is important to confirm our results. However, when combining data of VCP with those from other susceptible gene regions from previous association studies (i.e. TNFRSF11A, CSF1, OPTN and TM7SF4), independent effect of each gene region was found and the cumulative population attributable risk is 72.7%.

The majority of the genetic risk for Paget's disease of bone is explained by genetic variants close to the CSF1, OPTN, TM7SF4, and TNFRSF11A genes.

Paget's disease of bone (PDB) is one of the most frequent metabolic bone disorders (1-5%), next to osteoporosis, affecting individuals above age 55. Sequestosome1 mutations explain a part of the PDB patients, but still the disease pathogenesis in the remaining PDB patients is largely unknown. Therefore, association studies investigating the relationship between genetic polymorphisms and sporadic PDB have been performed to find the genetic risk variants. Previously such studies indicated a role of the OPG and RANK gene. The latter was recently confirmed in a genome-wide association study (GWAS) which also indicated the involvement of chromosomal regions harbouring the CSF1 and OPTN gene. In this study, we sought to replicate these findings in a Belgian and a Dutch population. Similar significant results were obtained for the single nucleotide polymorphisms and the haplotypes. The most significant results are found in the CSF1 gene region, followed by the OPTN and TNFRSF11A gene region (p values ranging from 1.3 × 10(-4) to 3.8 × 10(-8), OR = 1.523-1.858). We next obtained significant association with a polymorphism from the chromosomal region around the TM7SF4 gene (p = 2.7 × 10(-3), OR = 1.427), encoding DC-STAMP which did not reach genome-wide significance in the GWAS, but based on its function in osteoclasts it can be considered a strong candidate gene. After meta-analysis with the GWAS data, p values ranged between 2.6 × 10(-4) and 8.8 × 10(-32). The calculated cumulative population attributable risk of these four loci turned out to be about 67% in our two populations, indicating that most of the genetic risk for PDB is coming from genetic variants close to these four genes.

Paget's disease of bone: evidence for complex pathogenetic interactions.

OBJECTIVES: Paget's disease of bone (PDB), with a prevalence of 2 to 5% in Caucasians >55 years, is the second most frequent metabolic bone disease, after osteoporosis. PDB characteristics are bone lesions with an imbalanced bone remodeling, resulting in disorganized and nonfully fledged new bone. PDB etiology is not completely understood. In this review, current views on the etiology, clinical aspects, and PDB treatment are summarized and discussed. METHODS: The PubMed database was searched using the keywords PDB, sequestosome1 (SQSTM1), valosin-containing protein (VCP), receptor activator of nuclear factor-κB (RANK), osteoprotegerin (OPG), RANK ligand (RANKL), mutation, genetic variants, virus, osteosarcoma, bisphosphonates, and denosumab. RESULTS: Environmental evidence (e.g. viruses) and also genetic risk factors have been found for PDB. Until now, SQSTM1 was the only PDB-causing gene identified. However, PDB patients without SQSTM1 mutations seem to have susceptibility genetic polymorphisms in regions containing the CaSR, ESR1, TNFRSF11B (OPG), TNFRSF11A (RANK), CSF1 (M-CSF), OPTN, TM7SF4 (DC-STAMP), VCP, NUP205, RIN3, PML, and GOLGA6A genes, resulting in an increased risk of developing PDB. The nature of these genes indicates that the regulation of osteoclastogenesis is a key process in PDB pathogenesis. Furthermore, with the involvement of SQSTM1 and VCP in autophagy and in forming protein aggregates, this might also indicate that a disturbance of these processes might be a risk factor. CONCLUSIONS: Unraveling the PDB genetic background is instrumental to understanding the PDB pathogenesis and the role of slow viruses. Furthermore, it might make early detection and subsequently treatment of risk individuals possible.

Genome-wide association identifies three new susceptibility loci for Paget's disease of bone.

Paget's disease of bone (PDB) is a common disorder characterized by focal abnormalities of bone remodeling. We previously identified variants at the CSF1, OPTN and TNFRSF11A loci as risk factors for PDB by genome-wide association study. Here we extended this study, identified three new loci and confirmed their association with PDB in 2,215 affected individuals (cases) and 4,370 controls from seven independent populations. The new associations were with rs5742915 within PML on 15q24 (odds ratio (OR) = 1.34, P = 1.6 × 10(-14)), rs10498635 within RIN3 on 14q32 (OR = 1.44, P = 2.55 × 10(-11)) and rs4294134 within NUP205 on 7q33 (OR = 1.45, P = 8.45 × 10(-10)). Our data also confirmed the association of TM7SF4 (rs2458413, OR = 1.40, P = 7.38 × 10(-17)) with PDB. These seven loci explained ∼13% of the familial risk of PDB. These studies provide new insights into the genetic architecture and pathophysiology of PDB.

Genetic variation in the TNFRSF11A gene encoding RANK is associated with susceptibility to Paget's disease of bone.

RANK (receptor activator of nuclear factor-κB), encoded by TNFRSF11A, is a key protein in osteoclastogenesis. TNFRSF11A mutations cause Paget's disease of bone (PDB)-like diseases (ie, familial expansile osteolysis, expansile skeletal hyperphosphatasia, and early-onset PDB) and an osteoclast-poor form of osteopetrosis. However, no TNFRSF11A mutations have been found in classic PDB, neither in familial nor in isolated cases. To investigate the possible relationship between TNFRSF11A polymorphisms and sporadic PDB, we conducted an association study including 32 single-nucleotide polymorphisms (SNPs) in 196 Belgian sporadic PDB patients and 212 control individuals. Thirteen SNPs and 3 multimarker tests (MMTs) turned out to have a p value of between .036 and 3.17 × 10(-4) , with the major effect coming from females. Moreover, 6 SNPs and 1 MMT withstood the Bonferroni correction (p < .002). Replication studies were performed for 2 nonsynonymous SNPs (rs35211496 and rs1805034) in a Dutch and a British cohort. Interestingly, both SNPs resulted in p values ranging from .013 to 8.38 × 10(-5) in both populations. Meta-analysis over three populations resulted in p = .002 for rs35211496 and p = 1.27 × 10(-8) for rs1805034, again mainly coming from the female subgroups. In an attempt to identify the underlying causative SNP, we performed functional studies for the coding SNPs as well as resequencing efforts of a 31-kb region harboring a risk haplotype within the Belgian females. However, neither approach resulted in significant evidence for the causality of any of the tested genetic variants. Therefore, further studies are needed to identify the real cause of the increased risk to develop PDB shown to be present within TNFRSF11A.

Founder effect in different European countries for the recurrent P392L SQSTM1 mutation in Paget's Disease of Bone.

Paget's Disease of Bone (PDB) is one of the most frequent metabolic bone diseases, affecting 1-5% of Western populations older than 55 years. Mutations in the sequestosome1 (SQSTM1) gene cause PDB in about one-third of familial PDB cases and in 2.4-9.3% of nonfamilial PDB cases, with the 1215C-->T (P392L) mutation being the most frequent one. We investigated whether a founder effect of the P392L SQSTM1 mutation was present in Belgian (n = 233), Dutch (n = 82), and Spanish (n = 64) patients without a PDB family history. First, direct sequencing analysis of exon 8 in these three populations showed that the P392L mutation occurred in 17 Belgian patients (7.3%), three Dutch patients without a family history (3.7%), and two Dutch patients with a family history. In the Spanish population, 15.6% of patients (n = 10) had the P392L mutation, including one homozygous mutant. This is by far the highest mutation frequency of all populations investigated so far. Next, we examined the genetic background of 33 mutated chromosomes by analyzing haplotypes. We genotyped four single-nucleotide polymorphisms (SNPs) in exon 6 and the 3'-untranslated region of SQSTM1 (rs4935C/T, rs4797G/A, rs10277T/C, and rs1065154G/T) and used software programs WHAP and PHASE to reconstruct haplotypes. Finally, allele-specific primers allowed us to assign the mutation to one of the two haplotypes from each individual. Sequencing results revealed that all 33 P392L mutations were on the CGTG (H2) haplotype. The chance to obtain this result due to 33 independent mutation events is 3.97 x 10(-14), providing strong evidence for a founder effect of the P392L SQSTM1 mutation in Belgian, Dutch, and Spanish patients with PDB.