In unicellular organisms, intracellular inclusions of amorphous calcium carbonate (ACC) have been initially described in cyanobacteria and, later, in unicellular eukaryotes of Lake Geneva (Switzerland/France). Inclusions in unicellular eukaryotes ‒named micropearls‒ consist of hydrated ACCs, frequently enriched in Sr or Ba, displaying internal oscillatory zonations due to variations in the Ba:Ca or Sr:Ca ratios. The analysis of our database consisting of 1597 micropearl analyses from Lake Geneva and 34 from Lake Titicaca (Bolivia/Peru) has shown that a certain number of Sr and Ba-enriched micropearls from these lakes contain As in amounts measurable by EDXS. A Q-mode statistical analysis has confirmed the existence of five geochemically distinct morpho-chemical groups of As-bearing micropearls, among which a new category identified in Lake Geneva, where As is often associated with Mg. This new type of micropearl is possibly produced in a small (7-12 m size) bi-flagellated organism. Micropearls from Lake Titicaca, which contain Sr, are found in an organism very similar to Tetraselmis cordiformis, observed in Lake Geneva. Lake Titicaca micropearls contain higher As concentrations which can be explained by the high As concentration in the water of this lake. The ubiquity of the biomineralization process observed points to the need for better understanding of the role of amorphous or crystalline calcium carbonates in As cycling in surface waters.

Background/Objectives: This study aimed to compare the diagnostic accuracy of the Wells and Geneva scores, used with a 500 ng/mL D-dimer cutoff, along with the age-adjusted D-dimer (AADD), YEARS, and PEGeD algorithms in patients with and without COVID-19. The performance of various D-dimer thresholds was also evaluated. Methods: This retrospective study included patients who presented to the emergency department and underwent computed tomography pulmonary angiography (CTPA) for suspected pulmonary embolism (PE). The diagnostic performance of clinical prediction algorithms was compared between two groups. Results: We analyzed data from 1423 patients; PE diagnosis and COVID-19 positivity rates were 7.3% and 69.9%, respectively. In patients with COVID-19, the Wells score with a 500 ng/mL D-dimer threshold exhibited 97.22% sensitivity (95% CI: 80.53–100.00) and 4.99% specificity (95% CI: 3.58–6.39). Using AADD increased the specificity to 7.81% (95% CI: 6.08–9.54) while maintaining sensitivity at 97.22% (95% CI: 93.43–100.00); similar results were observed for the Geneva score. The YEARS algorithm exhibited 86.11% sensitivity (95% CI: 78.12–94.10) and 32.75% specificity (95% CI: 29.73–35.78), whereas the PEGeD algorithm exhibited 86.11% sensitivity (95% CI: 78.12–94.10) and 34.06% specificity (95% CI: 31.00–37.12). The YEARS and PEGeD algorithms demonstrated better performance in patients with COVID-19 in terms of specificity and accuracy. Conclusion: COVID-19 infection did not significantly affect the diagnostic performances of the clinical algorithms for PE. YEARS and PEGeD performed better in patients with COVID-19, making them preferable. Higher D-dimer thresholds improved specificity but increased the risk of missed PE diagnoses.