The Latin American Association of Volcanology (Asociación Latinoamericana de Volcanología, ALVO), founded in 2010 in Manizales, Colombia, is a non-profit organization dedicated to strengthening volcanology in the region. With more than 2000 members across 26 countries, ALVO is a community-driven association that encompasses a wide diversity of institutions and disciplines, and has progressively become a key facilitator of initiatives aimed at reducing volcanic risk in Latin America. This article provides an updated overview of the association, examining its historical development, organizational structure, and evolution over time. We review the main initiatives developed and supported by the association, including training and mobility programs, scientific meetings, and special issues in peer-reviewed journals, as well as ALVO's efforts to disseminate information and regional volcano science through multiple channels (e.g., social media, website, Gaceta ALVO newsletter). Finally, we offer reflections that frame ALVO's work in a global context and outline future directions that the association aims to explore. The experience of ALVO highlights the role that scientific networks in the Global South can play in strengthening capacity development, fostering collaboration, and addressing shared challenges in volcanic risk reduction. Abstract La Asociación Latinoamericana de Volcanología (ALVO), fundada en 2010 en Manizales, Colombia, es una organización sin fines de lucro dedicada a fortalecer la volcanología en la región. Con más de 2000 miembros en 26 países, ALVO es una asociación gestionada por la propia comunidad que alberga una amplia diversidad de instituciones y disciplinas, y que se ha convertido progresivamente en un facilitador clave de iniciativas orientadas a la reducción del riesgo volcánico en América Latina. Este artículo presenta una actualización detallada de la asociación, examinando su desarrollo histórico, su estructura organizativa y su evolución a lo largo del tiempo. Se describen las principales iniciativas desarrolladas y apoyadas por la asociación, incluyendo programas de formación y movilidad, reuniones científicas y números especiales en revistas con revisión por pares, así como los esfuerzos de ALVO por difundir información y conocimiento volcanológico regional a través de múltiples canales (p. ej., redes sociales, sitio web, Gaceta ALVO). Finalmente, se comparten algunas reflexiones que sitúan el trabajo de ALVO en un contexto global y delinean posibles líneas de acción futura que la asociación busca explorar. La experiencia de ALVO pone de relieve el papel que las redes científicas en el Sur Global pueden desempeñar en el fortalecimiento de capacidades, la promoción de la colaboración y el abordaje de desafíos compartidos en la reducción del riesgo volcánico.

The Central Andes of South America contains hundreds of composite volcanoes with a wide variety of morphologies and ages, making it a unique region to investigate the spatial, temporal and geomorphological evolution of arc volcanism. We present and analyze a database that includes new spatial, geomorphic and morphometric data, as well as relative and absolute age data, for 645 Late Oligocene to Holocene composite volcanoes and large lava domes of the Central Andes of Bolivia, Chile and Argentina (17.1 degrees-28.1 degrees S). The included volcano edifices show a great morphometric diversity, from small simple cones with volumes <= 1 km3 to complex, long-lived massifs with volumes of up to 300 km3. Quaternary edifices have lifespans mostly between 0.2 and 1.8 Myr, and average growth rates typically between 10 and 80 km3/Myr. The spatial distribution of volcanism highlights the influence of arc-oblique structures and of some first-order, continental and oceanic crustal anomalies. Cumulative bulk volumetric output estimates are of 12,000 km3 for the last -11.6 Myr, with an average output rate of 0.86 km3 per km of arc per Myr. Volumetric output peaks are centered at -19 degrees, 21.8 degrees, 24.2 degrees, 25.5 degrees, and 26.8 degrees S, each with variable inputs in terms of age and position with respect to the present-day arc. The database offers new opportunities for more detailed analyses of the spatial and/or temporal evolution of volcanism along different segments of the arc and for a variety of regional analyses in combination with geophysical, tectonic or geochemical datasets.

During 23 days in February 1984, the team made up by Wes Hildreth, Bob Drake, and Judy Fierstein explored and sampled much of the western half of the Tupungato volcano, a Chile-Argentina natural landmark at similar to 33.3 degrees S, including its summit area. The project remained unfinished, and this impressive, similar to 6,550 m-high volcanic edifice was no longer the focus of significant studies. Forty years later, Wes Hildreth has given up and graciously handed over to us all his data, so it can now be shared with the geological community. Bob Drake dated six samples of Tupungato through the K-Ar technique. In a dacite dome from the southern summit, interpreted as the youngest Tupungato activity, a hornblende age of 831 +/- 116 ka is reported. A long-standing controversy is thus resolved: Tupungato has no Holocene activity. 1.26 +/- 0.6 Ma to 932 +/- 90 ka plagioclase ages are reported from three andesite lavas from the lower to middle flank of the volcano, constraining the age of the edifice to the Early Pleistocene. Finally, hornblendes from two pre-Tupungato dacitic deposits at the volcano's western foothill were dated at 11.4 +/- 0.5 Ma and 9.45 +/- 0.6 Ma. These much older deposits may represent pyroclastic rich facies similar to the ones described in the upper sections of the Tunuyan Conglomerates, in Argentina.

Cordilleran arcs are built by long periods of steady-state magmatism punctuated by transient high-flux magmatic episodes or flare-ups. Such flare-ups, manifested as periods of prodigious silicic volcanism and magmatism, result from geodynamic perturbations that cause elevated rates of magma addition to the crust. Questions remain, however, about how magmatic addition rates quantitatively compare between steady-state and flare-up modes of arc magmatism, and how long after the major geodynamic perturbation the flare-up begins. Here, we compute new estimates of erupted volumes over the last 35 Myr for the 22.5–29°S segment of the Central Andes based on a new volcanic geospatial database. These yield magmatic addition rates at least an order of magnitude higher during flare-up compared to steady-state conditions. A lag time of ~8–12 Myr between ocean ridge subduction (the major geodynamic perturbation in the Central Andean arc) and the onset of flare-up conditions is estimated.

Background Anti-Jo-1 autoantibodies represent essential markers in the diagnosis of antisynthetase syndrome (ASS). In this retrospective study, we aimed to investigate whether their concentrations and fluctuations could both respectively reflect the severity and evolution of ASS. Methods Between 2015 and 2020, clinical and biological features of ASS patients with at least one positive measure of anti-Jo-1 autoantibody were collected. At each serum sampling, we assessed myositis activity by using the Myositis Intention to Treat Activities Index (MITAX) and compared anti-Jo-1 concentrations with ASS severity, anti-Jo-1 concentrations between patients with and without active disease, and changes in anti-Jo-1 concentrations with disease activity. Results Forty-eight patients with ASS had at least one positive determination of anti-Jo-1 concentration. Among them, twenty-nine patients had at least two determinations of anti-Jo-1 autoantibody in their follow-up. We showed that these autoantibody concentrations were significantly correlated with MITAX ( r = 0.4, p = 0.03) and creatine kinase concentration ( r = 0.34, p = 0.002) and that they were significantly higher in patients with active disease than in those with inactive disease (91.7 IU/L vs 44.4 IU/L, p = 0.016). During follow-up, we found a significant correlation between fluctuations of anti-Jo-1 autoantibody concentrations and MITAX score ( r = 0.7, p < 0.0001). Conclusion Our results suggest that anti-Jo-1 autoantibody concentration could be a predictive marker of the severity and evolution of ASS and show that their quantification could represent a precious tool for disease monitoring and for improving the therapeutic management of ASS patients.

Diagnosis is a key step of patient management. During decades, refined decision algorithms and numerical scores based on conventional statistic tools were elaborated to ensure optimal reliability. Recently, a number of machine learning tools were developed and applied to process more and more extensive data sets, including up to million of items and yielding sophisticated classification models. While this approach met with impressive efficiency in some cases, practical limitations stem from the high number of parameters that may be required by a model, resulting in increased cost and delay of decision making. Also, information relative to the specificity of local recruitment may be lost, hampering any simplification of universal models. Here, we explored the capacity of currently available artificial intelligence tools to classify patients found in a single health center on the basis of a limited number of parameters. As a model, the discrimination between systemic lupus erythematosus (SLE) and mixed connective tissue disease (MCTD) on the basis of thirteen biological parameters was studied with eight widely used classifiers. It is concluded that classification performance may be significantly improved by a knowledge-based selection of discriminating parameters.

The IAVCEI Working Group on Hazard Mapping has been active since 2014 and has facilitated several activities to enable sharing of experiences of how volcanic hazard maps are developed and used around the world. One key activity was a global survey of 90 map makers and practitioners to collect data about official, published volcanic hazard maps and how they were developed. The survey asked questions about map content, design, and input data, as well as about the map development process and key lessons learned. Here we present the results of this global survey, which are then used to quantitatively describe and summarise current practices in volcanic hazard map development. We received entries related to 89 volcanic hazard maps (78% long-term/background maps and 22% short-term/crisis hazard maps), covering a total of 80 volcanoes across 28 countries. Although most maps captured in the survey are volcano-scale maps of stratovolcanoes that show similar types of content, such as primary hazard footprints or zones, they vary greatly in input data, communication style, format, appearance, scale, content, and visual design. This diversity stems from a range of factors, including differences in map purpose, the methodology used, the level of understanding of past eruptive history, the prevailing scientific and cartographic practice at the time, the state of volcanic activity, and variations in culture, national map standards and legal requirements. Experiences and lessons shared by our respondents can be divided into six main themes: map design considerations; the process of map development; map audience and map user needs; hazard assessment approach; map availability and accessibility; and external (e.g., political) influences. Insights shared included the importance of: visual design elements, map testing and evaluation, working with stakeholders and end users to improve a map’s efficacy and relevance, and considering possible unanticipated uses of hazard maps. These free-form text insights (i.e., responses to open-ended questions) from map makers and practitioners familiar with the maps lend depth and clarity to our results. They provide a rich complement to our more quantitative analysis of design elements and of approaches used to determine and delineate map zones. Results from our global survey of hazard map makers and practitioners, together with insights from other key initiatives of the Working Group on Hazard Mapping such as the Volcanic Hazard Maps Database (VHMD; https://volcanichazardmaps.org/ ), provide a snapshot of the wide variety of volcanic hazard maps generated over the past decades, and improve our understanding of the diversity across volcanic hazard mapping practices. These initiatives represent important steps towards fulfilling the aims of the Working Group, namely, to construct a framework for a classification scheme for volcanic hazard maps and to promote harmonized terminology, as well as to identify and categorise good practices and considerations for volcanic hazard mapping.

The 180,000 km 2 of Arabian lava fields (“harrats” in Arabic) form one of the largest distributed basaltic provinces in the world. The most recent eruption in 1256 AD, on the outskirts of Medina, as well as shallow dike emplacement in 2009, ~ 200 km northeast of the city, suggest future volcanic threat to this area. Harrat Khaybar (~ 1.7 Ma to present) is one of the largest and most compositionally diverse Arabian lava fields; it is located ~ 137 km northeast of Medina and covers ~ 14,000 km 2 . Here, we present a new eruption event record and the first estimation of future potential locations and timing of volcanism in Harrat Khaybar. Volcanic vents and eruptive fissures were mapped using remote sensing and field studies, and categorized into a geospatial database, complemented by 16 new 40 Ar/ 39 Ar ages. Our analysis reveals that Harrat Khaybar developed over five eruptive phases, where vent locations over time focus towards the central axis forming a broad N-S trend, with a central group concentrated along an axis of the regional Makkah-Madinah-Nafud (MMN) line and wider spatial dispersion between vents outwards from there. For the whole field, we estimate a long-term average recurrence rate of ~ 2.3 eruptions per 10 kyr assuming a Poisson distribution for inter-event times, which indicates that Harrat Khaybar would belong to a global group of highly active distributed volcanic fields. Our analysis also reveals that the field likely had a “flare-up” period between 450 and 300 ka where the vast majority of eruptions occurred, with ~ 18 eruptions per 10 kyr. After this intense period, eruption rates fell to < 2 eruptions per 10 kyr. Based on our findings, we estimate cumulative probabilities of 1.09 and 16.3% as lower and upper bounds of at least one eruption occurring over the next 100 years somewhere in Harrat Khaybar, with the highest probabilities within the central axis region, in particular around Jabal Qidr, Bayda and Abyad.

Evaluation of volcanic hazards typically focusses on single eruptive centres or spatially restricted areas, such as volcanic fields. Expanding hazard assessments across wide regions (e.g., large sections of a continental margin) has rarely been attempted, due to the complexity of integrating temporal and spatial variability in tectonic and magmatic processes. In this study, we investigate new approaches to quantify the hazards of such long-term active and complex settings, using the example of the 22.5–28°S segment of the Central Volcanic Zone of the Andes. This research is based on the estimation of: 1) spatial probability of future volcanic activity (based on kernel density estimation using a new volcanic geospatial database), 2) temporal probability of future volcanic events, and 3) areas susceptible to volcanic flow and fall processes (based on computer modeling). Integrating these results, we produce a set of volcanic hazard maps. We then calculate the relative probabilities of population centres in the area being affected by any volcanic phenomenon. Touristic towns such as La Poma (Argentina), Toconao (Chile), Antofagasta de la Sierra (Argentina), Socaire (Chile), and Talabre (Chile) are exposed to the highest relative volcanic hazard. In addition, through this work we delineate five regions of high spatial probability (i.e., volcanic clusters), three of which correlate well with geophysical evidence of mid-crustal partial melt bodies. Many of the eruptive centres within these volcanic clusters have poorly known eruption histories and are recommended to be targeted for future work. We hope this contribution will be a useful approach to encourage probabilistic volcanic hazard assessments for other arc segments.

Uncertainty quantification (UQ) in eruption source parameters, like tephra volume, plume height, and umbrella cloud radius, is a challenge for volcano scientists because tephra deposits are often sparsely sampled due to burial, erosion, and related factors. We find that UQ is improved by coupling an advection‐diffusion model with two Bayesian inversion approaches: (a) a robust but computationally expensive Generalized Likelihood Uncertainty Estimation algorithm, and (b) a more approximate but inexpensive parameter estimation algorithm combined with first‐order, second‐moment uncertainty estimation. We apply the two inversion methods to one sparsely sampled tephra fall unit from the 2070 BP El Misti (Peru) eruption and obtain: Tephra mass 0.78–1.4 × 10 11 kg; umbrella cloud radius 4.5–16.5 km, and plume height 8–35 km (95% confidence intervals). These broad ranges demonstrate the significance of UQ for eruption classification based on mapped deposits, which has implications for hazard management.

Since the late-18th Century, eye-witness accounts have documented a wide-spectrum of eruptive activity sourced from Volc & aacute;n Calbuco located in northwest Patagonia. Despite these observations there is very little known about the eruptive products themselves that can account for this eruptive diversity. In this study, we examine the tephrostratigraphic record post-dating the interval 1578-1702 cal. yr BP, with emphasis on historical eruptions (i.e. <130 years, including the 2015 eruption) at proximal to medial distances (<16 km from source) to characterize the composition, distribution, volume and style of these units. At least 11 discrete tephra units are recognized which are in accord with documented eruptive activity between -1760 CE and 2015. Juvenile pyroclasts from these units span a narrow compositional range from basaltic-andesite to andesite (55-60 wt% SiO2), and contain plagioclase (71-73%), pyroxene (-21%), cristobalite (3-5%) and scarce olivine and Ti-magnetite (1-2%). The largest documented historic eruption occurred in 1893-95, and produced a thick mantle of coarse-grained tephra fallout (0.32-0.50 km3 non-DRE) accompanied by intense ballistic bomb barrage closer to source. The 1893-95 eruption is comparable to the 1961 and 2015 eruptions both in terms of magnitude and explosivity, despite pyroclastic density currents (PDCs) not being documented in 1893-95. Both the 1929 and 1961 eruptions generated lava-flows, tephra fallout and PDCs, from which the 1961 volume totalled -0.17 km3 non-DRE, affecting valleys northeast, up to a distance of 6 km from the crater. In contrast, the 2015 eruption only produced PDCs, tephra fallout and ballistics (0.26-0.36 km3 non-DRE). Results obtained from dendrochronological analysis of Nothofagus dombeyi trees within the study area reveals growth suppression indicated by structural damage during the 1893, 1929 and 1961 eruptions, probably related to thicker overall accumulations of tephra. Collectively, the componentry, architecture and volume of historic (AD 1893, 1961 and 2015) Calbuco tephra indicate sub-Plinian parental events derived from more mafic products with disequilibrium textures, than smaller eruptions characterized by c. 60% wt. SiO2 probably triggeredby crystal fractionation, providing a centennial time scale eruptive heterogeneity. This data is meaningful in terms of better understanding eruptive diversity at basaltic-andesite centers elsewhere that have high eruption frequencies (e.g. centennial time-scales). (c) 2021 Elsevier B.V. All rights reserved.

New stratigraphic, lithological and petrographic analyses of La Poruña scoria cone (21° 53′ S-68° 30′ W, Central Andes, northern Chile) allow the reconstruction of the eruptive sequence of this monogenetic cone. Petrographic and lithological characteristics allow us to identify three main lithostratigraphic units at La Poruña scoria cone. The first unit consists of agglutinated lapilli, spatter beds, and clastogenic lavas that are related to the construction of the cone. The other two units are associated with a lava flow field and consist of flow of andesitic composition, which differ both in their degree of weathering and in their development of channel, surface, and internal structures (e.g., levées, ogives, and joints). With these lithostratigraphic analyses, we interpret that the construction of La Poruña occurred during four main eruption phases involving Strombolian, Hawaiian, and transitional eruptive styles. Furthermore, differences in the degree of erosion, alteration, and weathering of the lithostratigraphic units in the lava field of La Poruña suggest that this flow field was formed during two eruptive events. The excellent outcrop conditions and preservation state of the volcanic products of La Poruña allow new stratigraphic insights that advance the wider and more general understanding and the dynamics of this important type of volcanism and the potential hazards of a scoria cone eruption. The polycyclic style of the eruption needs to be included in the hazards assessment of these centers type, especially when the cone is associated with structures that can be reactivated. This process could correspond to a second phase of activity, involving ash fall, bomb, and lava emission.

La Poruña (21°53′S; 68°30′W) is a 140 m high scoria cone composed of pyroclastic material and an extensive basaltic-andesite to andesite lava flow that is up to 8 km in length. Automated mineralogical analysis describes a suite of porphyritic mafic samples, comprising olivine- and pyroxene-bearing rocks. Well-defined major element compositional trends, as well as trace and rare earth element characteristics (e.g. Sr/Y < 47; Sm/Yb < 4), likely reflect magmatic differentiation at middle-upper crustal levels. Additionally, magma mixing and assimilation and fractional crystallization processes act on these La Poruña magmas within the thickened continental crust, which is typical in Andean volcanic systems. A remarkable compositional feature is the unusual reversed isotopic behaviour of increasing silica with decreasing 87Sr/86Sr compositions. In a process of crustal assimilation during turbulent magma ascent (ATA), the least differentiated rocks are the most contaminated ones since the turbulent hottest magmas effectively assimilate the crustal material. We relate the inverse Sr isotope trend to latter magmatic evolution involving ATA at shallow crustal levels prior to eruption, therefore differing from the broadly accepted Central Andean magmatic model. The older volcanics (>96 ka) from San Pedro volcano exhibit similar isotopic characteristics, therefore evidence of similar magmatic processes. This new dataset clearly defines magma compositional changes during the La Poruña eruption (ca. 100 ka), revealing an increase in crustal contamination at shallow crustal levels for the younger San Pedro lavas (<96 ka), likely controlled by increasing amounts of deep-sourced basaltic input over time.

Excel file containing sheets for different volcano-structural datasets for the CLV. (XLSX 36 kb)

This paper introduces an open source computer code to perform an integrated probabilistic spatio-temporal volcanic hazard assessment in distributed volcanic fields. The program, named MatHaz, is a set of Matlab scripts that follows a sequential methodology. After the user has provided a set of input files, this tool first estimates the spatial probability of future volcanic vents, then the temporal probability of future volcanic events, and finally models up to five volcanic phenomena (pyroclastic density currents, ballistic projectiles, lava flows, lahars, and tephra fallout) following a probabilistic approach. These results can be combined and depicted as an integrated quantitative (and/or qualitative) volcanic hazard map, with weightings of hazard factors chosen by the user. We illustrate the use of this tool by applying it to the Carrán-Los Venados Volcanic Field in southern Chile. The open-source, replicable, and user-friendly nature of the code allows its application to any volcanic region of the world, regardless of its extent, type, and amount of volcano-structural data.

Anti-signal recognition particle (SRP) antibodies are important serological markers for the diagnosis and the prognosis of idiopathic inflammatory myopathy (IIM), especially to distinguish immune-mediated necrotizing myopathy (IMNM). This study was set up to investigate the phenotype associated with anti-SRP antibodies and to evaluate the methods for detecting these antibodies. Clinical and biological data were retrospectively obtained from 60 adult patients with anti-SRP antibodies detected by a dot immunoassay from 12 centers. Thirty-six (60 %) out of these 60 patients suffered from an IIM, and among them, 21 patients were diagnosed as IMNM. Among patients with a definite IIM, proximal weakness and myalgia were prominent symptoms at the time of diagnosis. Only few patients displayed severe extra-muscular symptoms such as cardiac involvement or severe myositis. Mean creatine kinase levels were high for all patients except for two of them. When testing by indirect immunofluorescence (IIF) on HEp2 cells, the fraction of patients displaying the typical anti-SRP fine speckled staining of the cytoplasm was higher in patients with IIM (30/36) (83 %) than in patients with non-IIM (3/24) (12.5 %) (p < 0.0001). Thirty (91 %) out of 33 patients with a positive immunodot and a characteristic IIF cytoplasmic staining suffered from a clinical definite myositis, whereas only 6 (22 %) out of 27 patients with a positive immunodot but a negative cytoplasmic pattern suffered from a myositis (p < 0.00001). This series highlights the strong heterogeneity of anti-SRP positivity that encompassed IMNM and non-IMNM and supports the necessity of considering both IIF and dot immunoassay to confirm the diagnosis of anti-SRP-associated myositis.

The 10 day explosive phase of the 2008-2009 eruption of Chaiten volcano, Chile, draped adjacent watersheds with a few cm to >1 m of tephra. Subsequent lava-dome collapses generated pyroclastic flows that delivered additional sediment. During the waning phase of explosive activity, modest rainfall triggered an extraordinary sediment flush which swiftly aggraded multiple channels by many meters. Ten kilometer from the volcano, Chaiten River channel aggraded 7 m and the river avulsed through a coastal town. That aggradation and delta growth below the abandoned and avulsed channels allow estimates of postdisturbance traction-load transport rate. On the basis of preeruption bathymetry and remotely sensed measurements of delta-surface growth, we derived a time series of delta volume. The initial flush from 11 to 14 May 2008 deposited 0.5-1.5 x 10(6) m(3) of sediment at the mouth of Chaiten River. By 26 May, after channel avulsion, a second delta amassed about 2 x 10(6) m(3) of sediment; by late 2011 it amassed about 11 x 10(6) m(3). Accumulated sediment consists of low-density vesicular pumice and lithic rhyolite sand. Rates of channel aggradation and delta growth, channel width, and an assumed deposit bulk density of 1100-1500 kg m(-3) indicate mean traction-load transport rate just before and shortly after avulsion (similar to 14-15 May) was very high, possibly as great as several tens of kg s(-1) m(-1). From October 2008 to December 2011, mean traction-load transport rate declined from about 7 to 0.4 kg(-1) m(-1). Despite extraordinary sediment delivery, disturbed channels recovered rapidly (a few years).

Soon after the onset of an eruption, model forecasts of ash dispersal are used to mitigate the hazards to aircraft, infrastructure, and communities downwind. However, it is a significant challenge to constrain the model inputs during an evolving eruption. Here we demonstrate that volcanic lightning may be used in tandem with satellite detection to recognize and quantify changes in eruption style and intensity. Using the eruption of Calbuco volcano in southern Chile on 22 and 23 April 2015, we investigate rates of umbrella cloud expansion from satellite observations, occurrence of lightning, and mapped characteristics of the fall deposits. Our remote sensing analysis gives a total erupted volume that is within uncertainty of the mapped volume (0.56 +/- 0.28 km(3) bulk). Observations and volcanic plume modeling further suggest that electrical activity was enhanced both by ice formation in the ash clouds >10 km above sea level and development of a low-level charge layer from ground-hugging currents.

BACKGROUND:With the emergence of biotherapies, accurate diagnosis in early arthritis is needed. At this time, there is no biological marker of psoriatic arthritis.OBJECTIVE:To test whether antinuclear antibodies (ANA) can be used as a diagnostic tool in psoriatic arthritis (PsA), we evaluated the prevalence of ANA in biologic-naïve PsA patients and in healthy blood donors.METHODS:232 patients from the Rheumatology department, St Marguerite's Hospital, Marseilles, who fulfilled the CASPAR criteria for PsA, underwent clinical and laboratory investigations. Antinuclear antibodies (ANA), anti-extractable nuclear antigen antibodies (ENA), rheumatoid factor (RF), anti-citrullinated protein antibodies (ACPA) were assayed. Ninety-one healthy blood donors were also tested.RESULTS:Detection of ANA by indirect immunofluorescence was significantly more frequent in sera from PsA patients than those from controls at serum dilution of 1:100 (57% compared with 40%, Odds Ratio (OR) 1.98 (1.2-3.4) p<0.02) and 1:160 (52% compared with 24%, OR 3,7 (1.9-7.2) p<0.001). No patients had lupus specific autoantibodies, 15 % had RF (34/232), and 1.7 % had ACPA (4/232).CONCLUSIONS:Detection of ANA was more frequent in sera from PsA patients than in those from healthy controls. This suggests that ANA could be a diagnosis orientation tool in PsA. Nevertheless, the specificity of these antibodies still remains to be investigated.