Statistical hypothesis testing is one of the key steps in modern medical research. Initially, scientists formulate a research hypothesis based on which the statistical hypothesis is then developed and statistically tested. This review provides the null and alternative hypotheses’ compiling examples for different research questions and the general algorithm for their testing using t-test. The authors also describe type I errors, which are necessary to interpret p-values estimated from statistical tests, and type II errors, which are used to assess study power. The article focuses on effect size and its calculation methods, and the difference between statistically significant and clinically significant effects. The associations between effect size, sample size, and type II error are also discussed.

Aim. To evaluate antibody responses following two doses of ChAdOx1 nCoV-19 Corona vaccination in a tertiary care setting and the association of host factors like age, body mass index and comorbidities in determining this antibody response.

Materials and methods. This prospective serosurveillance study was done among healthcare workers of Jubilee Mission Medical College, vaccinated during January- April 2021. Blood samples were drawn from 170 participants after their first dose and from 156 participants after their second dose of Covishield^TM to measure the specific Ig G antibodies against the recombinant S1 subunit of the S protein of SARS-CoV-2.

Results. The median level of anti-SARS-CoV-2 Ig G antibody 28–56 days after the first dose vaccination was 3.64 S/C (1.33, 7.24) and 11.6 S/C (8.61, 14.27) after 14 days of second dose vaccination. Protective levels of anti-SARS CoV-2 Ig G antibodies (≥ 9.5 S/C) was developed by 25 participants (14.7%, 95% confidence interval: 9.8% to 20.9%) after 28–56 days of first dose of vaccination and by 109 participants (69.9%, 95% confidence interval: 62% to 77%) after 14 days of second dose. Health care workers in the age group below 60 years (p = 0.027) and without comorbidities (p = 0.079) showed higher protective Ig G levels. But on multiple logistic regression only age under 60 years was found to be statistically significant.

Conclusion. After the first dose of the ChAdOx1 nCoV-19 vaccine, the formation of Ig G antibodies was observed, the level of which increased after the second dose. Among the various associated factors studied only the age of the participants below 60 years was found to be statistically significant for protective antibody levels. Follow up studies involving larger and different ethnic population is key to decoding the antibody response especially in the elderly and high-risk groups.

Aim. To study the effect of simultaneous administration of creatine phosphate immediately before ischemia on cardiodynamic parameters and biomarkers of oxidative stress in the coronary venous blood flow during retrograde perfusion in an isolated rat heart.
Materials and methods. 20 Wistar albino rats were divided into 2 groups: group 1 (control) and group 2 (experimental), 10 rats per group. Cannulation and retrograde perfusion of aorta of an isolated rat heart with Krebs–Henseleit buffered solution by Landendorff was performed. Both groups underwent ischemia-reperfusion injury, which included global ischemia for 20 minutes followed by reperfusion for 30 minutes. The group 2 (experimental) was preconditioned with creatine phosphate at a dose of 0.2 mmol/l for 5 min before ischemia. We registered cardiodynamic parameters and indicators of oxidative stress at the point of stabilization, at the 1st and 30th minutes of reperfusion.
Results. With the impact of creatine phosphate at the 30th minute of reperfusion in the group 2 in comparison with group 1, there was found an increase in the maximum and minimum speed of pressure elevation in the left ventricle (1.7 and 1.9 times, respectively), and of systolic and diastolic pressure in the left ventricle (1.5 and 1.6 times, respectively). Biomarkers of oxidative stress (lipid peroxidation index, nitrites, superoxide anion radical and hydrogen peroxide) were also statistically significantly lower in the group 2 after the 1st minute of reperfusion (by 1.2 times, by 1.4 times, by 2.8 times and 1.9 times, respectively), and after the 30th minute (1.3 times, 2.1 times, 1.9 times and 2.1 times, respectively).
Conclusion. The administration of creatine phosphate into the coronary flow 5 minutes before the onset of ischemia has a protective effect on myocardial contractility. Reduction of oxidative stress and damage can be considered as a protective effect of creatine phosphate.

DRESS syndrome is a life-threatening complication rarely encountered in clinical practice. Making a correct diagnosis is complicated not only by the similarity of the clinical manifestation with several other conditions but also delayed in time onset of the first symptoms from the “causative” drug. Along with that, timely diagnosis and early treatment reduce the risk of severe course and complications of the syndrome.
Clinical case. A 29-year-old female patient was admitted to the hospital due to generalized maculopapular rash, fever, generalized lymphadenopathy, fatigue, splenomegaly appeared after adding meropenem to carbamazepine therapy. Blood tests showed leukocytosis – 33.6×109/l, hypereosinophilia – 7.9×109/l, elevated liver transaminases. After exclusion of autoimmune, infectious and oncohematological diseases the diagnose of DRESS syndrome was established. On the background of methylprednisolone therapy at the dose of 1 mg/kg fast normalization of body temperature, disappearance of rash, decrease in eosinophils were observed.
Discussion. The specific feature of this clinical case is the development of DRESS syndrome after adding antibiotic to anticonvulsant drug (with which this syndrome is commonly associated). This fact complicated the diagnosis. Raising doctors’ awareness about the possibility of developing such an adverse reaction to antibiotic therapy seems to be extremely important to improve the prognosis of this group of patients.

The aim. Demonstrate a novel modality of laser-scanning multiphoton microscopy suitable for rapid acquisition of images of samples labelled with phosphorescent materials characterised by long emission lifetime measured in microseconds. The reported microscopy represents an advancement over the existing laser-scanning modalities, where the acquisition of images of phosphorescent materials takes unpractically long time.
Materials and methods. The reported method is based on rapid scanning of the focussed excitation beam across a sample while continuously recording the photoluminescent (PL) signal. The resultant images of discrete phosphorescent nanoparticles appeared blurred. The diffraction-limited image was reconstructed by using a deconvolution algorithm, where the PL lifetime was the key input parameter. To test the method, two types of upconversion nanoparticles (UCNP) were synthesised, NaYF₄:Yb³+:Er³+/NaYF₄ (E-UCNP), β-NaYF₄:Yb³+, Tm3+/NaYF₄ (T-UCNP) and used to test a possibility of demultiplexing the two types of UCNPs ex vivo taken up in the mouse liver.
Results. The resultant images of E-UCNP, T-UCNP on the background of the liver were fully reconstructed and exhibited the enhanced signal-to-noise ratio. Besides, the method allowed rapid (at the scale of seconds) acquisition of the UCNP PL lifetime and clear discrimination of the two types of UCNPs.
Conclusion. We demonstrated a new approach for rapid PL image acquisition of samples containing PL materials, such as biological specimens labelled with discrete UCNPs. Blurred images were shown to be reconstructed at the post-processing stage by applying a deconvolution procedure. This enabled demonstration of multiplexing/demultiplexing using lifetime imaging mode, where the lifetime was engineered by the UCNP synthesis and reconstructed during multiphoton image acquisition using the deconvolution algorithm. The power of this method was demonstrated by the identification of two types of UCNPs accumulated in the liver of a laboratory animal. We believe that the demonstrated method can be useful for rapid lifetime imaging where several molecular specific labelling agents are required.