When rare becomes common: N2 gene-positive, E gene-negative SARS-CoV-2 PCR results between 2021 and 2022

Nucleocapsid gene-positive, envelope gene-negative (N2+/E-) SARS-CoV-2 PCR results obtained with the Cepheid Xpert Xpress SARS-CoV-2 assay are an infrequent phenomenon. We assessed the validity of the N2+/E- cases with an indirect approach by analyzing their occurrence in relation to overall positive PCR rates and absolute number of PCR tests (24,909 samples, collected June 2021 to July 2022). Additionally, 3022 samples were analyzed with the Xpert Xpress CoV-2-plus assay in August/September 2022. The incidence of monthly N2+/E- cases closely followed the overall frequency of positive tests (p < 0.001), while there was no correlation with the monthly number of PCR test. The observed distribution of N2+/E- cases implicates, that they are not merely artefacts, but rather represent samples with a very low viral load. This phenomenon will persist with the Xpert Xpress SARS-CoV-2 plus assay, which also produced more than 10% results where only one target gene replicated with a very high Ct value.

Comparison of three different protocols for obtaining hemolysis

OBJECTIVES

Hemolysis is associated with erroneous or delayed results. Objectives of the study were to compare four different methods for obtaining hemolysis in vitro on three different analyzers.

METHODS

Hemolysis was prepared with addition of pure hemoglobin into serum pool, osmotic shock, aspiration through blood collection needle, freezing/thawing of whole blood. Biochemistry parameters were measured in duplicate at Architect c8000 (Abbott, Abbott Park, USA), Beckman Coulter AU680 (Beckman Coulter, Brea, USA) and Cobas 6000 c501 (Roche, Mannheim, Germany), according to manufacturers' declarations. Cut-off value was defined as the highest value of H index with corresponding bias lower than acceptance criteria.

RESULTS

We were not able to obtain results with freezing protocol. On all three platforms, lowest number of analytes were sensitive to hemolysis at H=0.5 using method of adding free hemoglobin. When osmotic shock was used, cut-off values for the most analytes were generally met at lower values. Hemolysis significantly interfered with measurement of potassium and lactate dehydrogenase (LD) at H=0.5 on all platforms. The most of the tested analytes had the lowest acceptable H index when aspiration method was used. At the low level of hemolysis (H=0.8) glucose, sodium, potassium, chloride, phosphate, and LD were affected on all analyzers, with some additional analytes depending on the manufacturer.

CONCLUSIONS

Hemolysis interference differs on different analyzers and according to protocol for obtaining hemolysis. Aspiration method was generally the most sensitive to hemolysis interference, while addition of free Hb was the most resistant.

Test validation, method comparison and reference range for the measurement of β-hydroxybutyrate in peripheral blood samples

Introduction

The measurement of β-hydroxybutyrate (βOHB) concentrations is a corner stone of the diagnosis of diabetic ketoacidosis and other ketonic states. The aim of this study was to perform a validation of a peripheral blood βOHB assay (Randox) on a Roche cobas c502 analyser and to establish a βOHB reference range for the validated assay.

Materials and methods

Precision, linearity and limit of detection and blank (LoD, LoB) were determined according to Clinical and Laboratory Standards Institute (CLSI) EP05-A3, EP 06-A and EP17-A2 guidelines, using commercial control material and residual patient sample pools. As method comparison, for 190 semi-quantitative measurements of urine ketones we determined the corresponding βOHB blood concentration. The reference range was based on the CLSI C28-A3 guideline, using 304 randomly selected serum samples from population based German National Cohort (GNC) study.

Results

Coefficients of variation for the validated assay ranged from 1.5% for high concentrations (3.1 mmol/L) to 6.5% for low concentrations (0.1 mmol/L). Detection capacity was LoB = 0.011 mmol/L and LoD = 0.037 mmol/L. Linearity of the assay ranged from 0.10 to 3.95 mmol/L. The agreement between the semi-quantitative urine ketone test and the βOHB blood test was moderate (Kappa = 0.66). The obtained 95% serum reference range was estimated as 0.02 to 0.28 mmol/l βOHB.

Conclusions

The Ranbut βOHB assay showed good precision and analytical performance. Our results confirm that βOHB measurement in peripheral blood is indeed a preferable alternative to the semi-quantitative measurement of urine ketones.

Croatian laboratories have a good knowledge of the proper detection and management of hemolyzed, icteric and lipemic samples

Endogenous interferences are an important source of biased laboratory results. Hemolysis, lipemia and icteria are the main source of endogenous interference in laboratory medicine. Accreditation according to ISO 15189 improves the overall quality of the laboratory procedures. The aim of our study was i) to assess the level of knowledge of Croatian medical biochemists about the proper detection and management of hemolysis, lipemia and icteria; and ii) to identify possible differences in the level of knowledge respective to the laboratory accreditation status.

An on-line self-report survey was carried out by the Working Group for Preanalytical Phase of the Croatian Society of Medical Biochemistry and Laboratory Medicine during April to May 2015. Survey included 14 statements (Q1–Q14) about procedures for samples with interferences and participants were asked to assess the degree of agreement with the statement using a 4-point Likert scale.

The lowest level of knowledge was observed for statements Q10 (dealing with icteric sample; 40.9% participants agreed with the correct procedure), Q12 (allowable error for interference; 47.2%) and Q11 (dealing with lipemic sample; 60.1%). Almost all participants (97.4%) agreed that laboratories in Croatia should have a harmonized protocol for management of samples with interferences. Participants from accredited laboratories showed higher knowledge of hemolysis detection (p=0.031), rejection of hemolyzed sample (p<0.001), management of icteric samples (p=0.038) and allowable error for interferences (p=0.040).

Croatian laboratories have a good knowledge of the proper detection and management of hemolyzed, icteric and lipemic samples. Accreditation is associated with higher knowledge about management of samples with interferences.

Serum omentin-1 levels as a possible risk factor of mortality in patients with diabetes on haemodialysis

AIM

The main cause of mortality in haemodialysis (HD) patients is cardiovascular disease. Serum omentin-1 level was found to be associated with cardio-metabolic disorders. The aim of this study was to examine the role of omentin-1 as a predictor of mortality in a group of diabetes positive HD patients.

METHODS

A total of 120 prevalent HD patients were included in the study from December 2012 to May 2014. Patients were divided into two groups according to the presence or absence of diabetes. Venous blood samples were taken at months 0 and 18 following an overnight fast (prior to a midweek HD session). Serum omentin-1 level was assessed by enzyme-linked immunosorbent assay.

RESULTS

A total of 84 HD patients were analysed at the end of an 18-month follow-up. Omentin-1 levels of HD patients with diabetes were found to be lower than of HD patients without diabetes (9.1±5.8 ng/mL vs. 11.4±4.1 ng/mL, respectively; P=0.015) at the end of follow-up. Omentin-1 levels of survived patients with diabetes were found to be higher than of nonsurvived patients with diabetes (16.5±10.1 ng/mL vs. 12.9±5.3 ng/mL, respectively; P=0.045). During follow-up, 36 patients (30%) died, of whom 25 had diabetes (34%).

CONCLUSIONS

Serum omentin-1 levels were significantly lower in HD patients with diabetes. A decrease in omentin-1 levels could be an independent mortality risk factor in this patient group. Further investigation in a greater number of patients is needed.

How well are pregnant women in Croatia informed about the oral glucose tolerance test?

INTRODUCTION

Preanalytical errors still constitute the largest source of errors in laboratory work. Proper patient preparation and patient's knowledge about a particular procedure affects its accuracy and reliability. We hypothesized that most of pregnant women are not well enough informed about the proper procedure for the OGTT. The aims of this study were to investigate: (i) how well pregnant women are informed about the OGTT; (ii) the most common way to inform pregnant women about OGTT and (iii) whether pregnant women's level of knowledge about the OGTT differ regarding source of information.

MATERIALS AND METHODS

The anonymous questionnaire was conducted across the country in 23 Croatian primary and secondary healthcare centres. The questionnaire contained 9 questions on certain demographic data and familiarity with OGTT procedure. All 343 participants filled the questionnaire before the first blood draw.

RESULTS

42% of the participants demonstrated high and 38% adequate level of knowledge about the OGTT procedure. Majority of participants were informed about the procedure by gynaecologist (56%). The level of knowledge differed among participants with different sources of information (P=0.030). Further analysis showed that the level of knowledge was lower in pregnant women having received information from their gynaecologist compared to pregnant women who received information from the laboratory staff.

CONCLUSIONS

In general, pregnant women are familiar with OGTT procedure, main source of information about the OGTT procedure is their gynaecologist, but the level of knowledge was higher in women who received information about the OGTT procedure from the laboratory staff.

Evaluation of the BD Vacutainer(®) RST blood collection tube for routine chemistry analytes: clinical significance of differences and stability study

Introduction:

Preanalytical variables account for most of laboratory errors. There is a wide range of factors that affect the reliability of laboratory report. Most convenient sample type for routine laboratory analysis is serum. BD Vacutainer^® Rapid Serum Tube (RST) (Becton, Dickinson and Company, Franklin Lakes, NJ, USA) blood collection tube provides rapid clotting time allowing fast serum separation. Our aim was to evaluate the comparability of routine chemistry parameters in BD Vacutainer^® RST blood collection tube in reference with the BD Vacutainer^® Serum Separating Tubes II Advance Tube (SST) (Becton, Dickinson and Company, Franklin Lakes, NJ, USA).

Materials and methods:

Blood specimens were collected from 90 participants for evaluation on its results, clotting time and stability study of six routine biochemistry parameters: glucose (Glu), aspartate aminotransferase (AST), alanine aminotransferase (ALT), calcium (Ca), lactate dehidrogenase (LD) and potassium (K) measured with Olympus AU2700 analyzer (Beckman Coulter, Tokyo, Japan). The significance of the differences between samples was assessed by paired t-test or Wilcoxon Matched-Pairs Rank test after checking for normality.

Results:

Clotting process was significantly shorter in the RSTs compared to SSTs (2.49 min vs. 19.47 min, respectively; P < 0.001). There was a statistically significant difference between the RST and SST II tubes for glucose, calcium and LD (P < 0.001). Differences for glucose and LD were also clinically significant. Analyte stability studies showed that all analytes were stable for 24 h at 4 °C.

Conclusions:

Most results (except LD and glucose) from RST are comparable with those from SST. In addition, RST tube provides shorter clotting time.

Brief history of medicine in Slovenia

Slovenes have lived in the territory of today's Slovenia for more than 14 centuries, whilst the history of its medical culture goes back for 2000 years. The advent of Christianity in Slovenia in the eighth century AD marked an important turning point in the development of its medicine. The 500 years of the Habsburg monarchy was later to have a further impact on the development of new medical ideas. During the Renaissance, the names of the Slovene doctors Mattioli, Paracelsus, Scopoli and Hacquet, who worked among Slovenians, were to become known all over Europe. Others of Slovene origin were Perlach, Santorio, Gerbezius, Carbonarius, Plenciz, and Sagar, whose work influenced European medical culture, especially in German speaking countries. However their Slovene nationality was not acknowledged until the second half of the 19th century.

13-cis-retinoic acid and bone density

BACKGROUND

13-Cis-retinoic acid has an influence on bone in patients on long-term treatment as well as on short-term treatment. The presence of skeletal abnormalities after the treatment was established by roentgenologic and scintigraphic examinations. We wanted to know whether a 6-month course of low-dose 13-cis-retinoic acid has a clinically important influence on bone density in men with severe acne.

METHODS

We examined 15 men with severe acne before and after treatment with 13-cis-retinoic acid by dual-photon absorptiometry of the lumbar spine.

RESULTS

The mean increase in bone density was 3.0% (95% confidence interval 1.3-4.5), which is normal for the period from puberty to late twenties. Bone density increased in 13 of our 15 patients.

CONCLUSIONS

As shown by this highly sensitive modern densitometric method, 13-cis-retinoic acid has no clinically important influence on bone density in male patients with severe acne.

Antihypertensive effect of indapamide given in conjunction with captopril in severe hypertension

The efficacy of captopril alone or in combination with indapamide was evaluated in 17 patients with severe hypertension (diastolic greater than 120 mmHg) previously treated with triple antihypertensive therapy, i.e. diuretic, beta-blocker and a vasodilator. After a wash-out period of 1 week, captopril was given initially as 75 mg/day for 2 weeks; at the end of this period, the dosage was doubled to 150 mg/day and continued at this level for a further 2 weeks. Indapamide (2.5 mg/day) was then added to the regimen and administered for 1 month. The results showed that captopril alone lowered, but did not normalize the blood pressure. The mean diastolic pressure was reduced to 117 and 103.8 mmHg after dosages of captopril of 75 mg and 150 mg, respectively. On the addition of indapamide, the blood pressure was normalized to 93.82 mmHg mean diastolic pressure. Systolic readings were similarly reduced. Two patients developed skin rashes while on captopril alone: no other treatment-related side-effects were reported once indapamide therapy had commenced.