The capacity and efficiency of the COVID-19 surveillance system in diagnosis patients by epidemiologic indicators are critical for system utility and practice. Policymakers and health managers can make effective plans to control the COVID-19 outbreak by having valid and appropriate data surveillance ability. They can also review and revise the plan, if necessary. Sensitivity, specificity, positive, and negative predictive value are important indicators for assessing the capacity of the surveillance system to diagnose cases. However, due to the low sensitivity of COVID-19 diagnostic tests and the high false-negative percentage and the long interval between the diagnosis and the confirmed result, it is better to evaluate the capacity of the surveillance system to take care of reliability indicators such as Percent Positive Agreement (PPA) and KAPPA STATISTICS.

Introduction: Leptospirosis is a significant public health problem in the Caspian littoral of Iran comprising Gilan, Mazandaran, and Golestan provinces. In Golestan province, serology assays indicated anti-Leptospira antibodies in animals and humans; however, no reliable record of infections in patients with signs and symptoms of the disease is available. Methods: We employed the indirect immunofluorescent antibody assay (IFA), and two PCR assays, a realtime PCR (qPCR) and a nested-PCR targeting 16S rDNA (rrs) sequence for diagnosis of leptospirosis in febrile patients in Golestan province. Results: Out of 52 febrile patients, 25 (48. 07%) had antibody titers ≥ 1/80 by IFA, and were defined as positive. In 7, 9, and 7 individuals, the antibody titers were 1/40, 1/20, and 1/10, respectively, and 4 had no antibodies. The qPCR and nested PCR detected leptospiral DNA in 55. 75% and 67. 3% of the patients' sera, respectively. The two PCR assays had a KAPPA agreement of 0. 53 (P< 0. 0001), suggesting a moderate agreement, and showed a significant reverse association with the IFA titers (P<0. 05). Conclusion: Our results suggest that higher antibody titers accompanied the spirochete's removal from blood by the patient's immune response. Hence, a reliable diagnosis of Leptospira infection necessitates deploying a DNA-based method alongside serology.

Descriptive STATISTICS is the process of summarizing gathered raw data from a research and creating useful STATISTICS, which help the better understanding of data. According to the types of variables, which consist of qualitative and quantitative variables, some descriptive STATISTICS have been introduced. Frequency percentage is used in qualitative data, and mean, median, mode, standard deviation; standard error, variance, and range are some of the STATISTICS which are used in quantitative data. In health sciences, the majority of continuous variables follow a normal distribution. skewness and kurtosis are two STATISTICS which help to compare a given distribution with the normal distribution.

A group $G$ is existentially closed (algebraically closed) if every finite system of equations and in-equations that has coefficients in $G$ and has a solution in an overgroup $H\geq G$ has a solution in $G$. Existentially closed groups were introduced by W. R. Scott in 1951. B. H. Neumann posed the following question in 1973: Does there exist explicit examples of existentially closed groups? Generalized version of this question is as follows: Let $\KAPPA$ be an infinite cardinal. Does there exist explicit examples of $\KAPPA$-existentially closed groups? Recently an affirmative answer was given to Neumann's question and the generalized version of it, by Kaya-Kegel-Kuzucuo\u{g}lu. We give a survey of these results. We also prove that, there are maximal subgroups of $\KAPPA$-existentially existentially closed groups and provide some information about subgroups containing the centralizer of subgroups generated by fewer than $\KAPPA$-elements. This generalizes a result of Hickin-Macintyre.