Nasopharyngeal Panbio COVID-19 Antigen Performed at Point-of-Care Has a High Sensitivity in Symptomatic and Asymptomatic Patients With Higher Risk for Transmission and Older Age

BACKGROUND

Performance of point-of-care tests in different clinical scenarios and on different samples remains undetermined. We comprehensively evaluated the performance of the nasopharyngeal Panbio COVID-19 Ag Rapid Test Device.

METHODS

This is a prospective study that includes consecutive patients attending 3 primary care centers (PCCs) and an emergency department. The antigen test was performed at point-of-care in nasopharyngeal and nasal swabs and in saliva. Positive percent agreement (PPA) and negative percent agreement (NPA) were calculated with the reverse-transcription polymerase chain reaction (RT-PCR) assay as reference standard.

RESULTS

Of 913 patients included, 296 (32.3%) were asymptomatic and 690 (75.6%) came from the PCC. Nasopharyngeal swabs were collected from 913 patients, nasal swabs were collected from 659 patients, and saliva was collected from 611 patients. The RT-PCR was positive in 196 (21.5%) nasopharyngeal samples (NPS). Overall, PPA (95% CI) in NPS was 60.5% (53.3-67.4), and it was lower in nasal swabs (44.7%) and saliva (23.1%). Test performance in NPS was largely dependent on the cycle threshold (Ct) in RT-PCR, with PPA of 94% for Ct ≤25 and 80% for Ct <30. In symptomatic patients, the PPA was 95% for Ct ≤25, 85% for Ct <30, and 89% for the symptom triad of fever, cough, and malaise. Performance was also dependent on age, with a PPA of 100% in symptomatic patients >50 years with Ct <25. In asymptomatic patients, the PPA was 86% for Ct <25. In all cases, NPA was 100%.

CONCLUSIONS

The nasopharyngeal Panbio COVID-19 Ag test performed at point-of-care has a good sensitivity in symptomatic patients with Ct <30 and older age. The test was useful to identify asymptomatic patients with lower Ct values.

Diet quality and nutrient density in subjects with metabolic syndrome: Influence of socioeconomic status and lifestyle factors. A cross-sectional assessment in the PREDIMED-Plus study

BACKGROUND

Socioeconomic disparities and lifestyle factors are likely to determine the overall quality of the diet. In addition, overeating is compatible with inadequate micronutrient intake and it can lead to adverse health outcomes.

OBJECTIVE

To assess adequacy of dietary nutrient intake and to investigate the influence of socioeconomic and lifestyle factors on nutrient density in a large primary cardiovascular prevention trial conducted in healthy participants with metabolic syndrome (MetS) to assess the cardiovascular effects of an energy-restricted Mediterranean diet (PREDIMED-Plus).

METHODS

Baseline cross-sectional analysis of the PREDIMED-Plus trial with 6646 Spanish participants (aged 55-75 years in men and 60-75 years in women) with overweight/obesity and MetS. Energy and nutrient intake (for 10 nutrients) were calculated using a validated 143-item Food Frequency Questionnaire (FFQ) and nutrient density was estimated dividing the absolute nutrient intake by total energy intake. The prevalence of inadequate intake was estimated according to dietary reference intakes. Multivariable linear regression models were fitted to examine associations between socioeconomic status or lifestyle factors and nutrient density.

RESULTS

A considerable proportion of the screened participants showed a deficient intake of vitamins A, D, E, B₉, calcium, magnesium and dietary fibre. Inadequate intake of four or more of the ten nutrients considered was present in 17% of participants. A higher nutrient density was directly and significantly associated with female sex, higher educational level and a better adherence to the Mediterranean diet. Lifestyle factors such as non-smoking and avoidance of sedentary lifestyles were also independently associated with better nutrient density.

CONCLUSIONS

Patients with MetS, despite being overweight, exhibited suboptimal nutrient intake, especially among men. Low nutrient density diet can be largely explained by differences in socioeconomic and lifestyle factors. These results highlight the importance of focussing on nutritional education in vulnerable populations, taking into account nutrient requirements.

Comparison of elasticities of components of a cardiac bioprosthesis leaflet

The mechanoelastic behavior of calf pericardium employed in cardiac bioprostheses was compared with that of three types of thread (Nylon, Prolene, and silk) used to suture this biological tissue. The elastic limit (EL) of each material was determined by means of tensile tests and the mathematical functions that govern the stress/strain curves within the EL have been described. The first derivative of these functions for each point to the curves allowed the immediate calculation of the elastic modulus (EM), which was considered the best parameter for comparing the elasticities of the materials being assessed. It was observed that the deformation of the pericardium produced by the working stress of a pericardial leaflet was approximately 1000 times greater than that produced in the surgical threads. When the elasticities were compared on the basis of the EM, that of pericardium was 749.06, 626.95, and 1253.17 times greater than that of the Nylon, Prolene, and silk suture threads, respectively. These results demonstrate that the interaction between these materials (pericardium and the threads) could be generating detrimental forces that can diminish the durability of the leaflets of the bioprostheses constructed of calf pericardium.

Description of the mathematical law that defines the relaxation of bovine pericardium subjected to stress

A material subjected to traction stress increases in length; if we maintain the elongation constant, the stress varies over a period of time. This phenomenon has been referred to as relaxation. The purpose of this study was to define a mathematical law that relates the variation in stress to time when elongation remains constant in bovine pericardium. The mathematical function obtained after assaying 34 samples to the point of relaxation, subjected to initial stresses ranging from 0.17-10.07 MPa, responds to the following equation: y = -0.0252 + 0.953 alpha - (0.0165 + 0.015 alpha)lnt, where y is the stress withstood at an instant in time, t, after initial stress alpha. A normogram, validated by assays of up to 6,340 min duration (4.40 days), is presented for graphic calculation, permitting the computation of the loss of stress due to relaxation of this biomaterial, with initial stresses ranging from 1-10 MPa.

Effect of the suture on the durability of bovine pericardium used in cardiac bioprostheses

Our study of the different biomaterials used in the construction of biological cardiac prostheses has shown it to be of vital importance that the physical properties of the tissue and of the suture that anchors it to the rigid polymeric support are compatible. By means of dynamic tests, we have determined the fatigue curve in sutured bovine pericardial tissue, expressed by the equation log y = 1.27 +/- 0.18 (0.26 +/- 0.05) log t, where y is the initial fatigue stress (MPa) and t is the time (min) it takes to achieve permanent deformation of the tissue. By applying this correction, we determine a set of values for stress-time which, when compared with those obtained with a non-sutured sample, reveal a significant fall in this ratio and, thus, a decrease in the durability. The use of suture threads of lesser elasticity than the pericardium may play an important role in reducing the durability of the bioprosthesis constructed with these materials.

Behaviour of the bovine pericardium used in cardiac bioprostheses when subjected to a real fatigue assay

The behaviour of bovine pericardium was studied using a fatigue assay. Twenty-three samples were assayed, maintaining the preset initial stress and measuring the time it took for the onset of load loss due to permanent deformation. The results indicated a mathematical relationship defined by the expression: log y = 1.3 - 0.211 log t, where y is the fatigue stress (MPa) and t the duration of the assay. The correlation coefficient was 0.948 (P < 0.001). The safety coefficient of the material diminished significantly as the period of time during which it was subjected to fatigue increased. The theoretical durability of the tissue was much greater than the real durability of the prostheses, which is determined by unsolved problems such as calcification and those derived from suture-related cutting.

Is cutting stress responsible for the limited durability of heart valve bioprostheses?

The limited durability of the valve bioprostheses made from calf pericardium is partially due to the calcification of this biomaterial and to mechanical fatigue of the tissue. The object of this study is to determine the harmful effect on the pericardial membrane of cutting caused by the suture thread by showing the different elastic behaviors of the biomaterials employed. This cutting stress is established during the process of molding the valve leaflet, creating a vulnerable point from the very moment of construction, which is an important factor in the limited duration of the bioprosthesis.

The relationship between stress and relaxation in calf pericardium used in the construction of cardiac bioprostheses

Assessment of relaxation (loss of load within a given time) without apparent deformation is a necessary step before durability assay of biomaterials. From results obtained using calf pericardium, the following conclusions were drawn: (a) there is no limit to relaxation for this biomaterials; (b) the lesser the load applied, the greater the relaxation; and (c) the relaxation curve follows the logarithmic function y = K1 - K2 - Int. These findings demonstrate the poor behaviour of the biomaterial at supposedly low loads and suggest that rupture-point load is not a reliable reference to determine the safety coefficient of calf pericardium used in cardiac bioprostheses.