Epidemiological Surveillance of Blood Donors in Kinshasa, 2014 - 2018.

BACKGROUND: The systematic detection of HIV, hepatitis B (HBV) and C (HCV) viruses in any blood donor has been in effect at the University hospital of Kinshasa since 2005. However, no data on the monitoring of blood donors is available today. The purpose of this thesis was to draw up the sero-epidemiological assessment of the afore-mentioned virus during the period 2014 - 2018. METHODS: This is an observational study conducted in the University Hospital of Kinshasa donor population. RESULTS: A total of 9,128 blood donors were admitted to the Kinshasa University Clinics Blood Bank during the period from 01/01/2014 to 12/31/2018 for 11,054 blood donations. The highest attendance (50%) of blood donors was observed in 2014 and 2015. On the other hand, 2018 (11.9%; n = 1,085) was that of the lowest frequency of blood donors. The mean age of the blood donors was 34.72 ± 10.66 years. The minimum and maximum age corresponded to 16 years and 65 years, respectively. The median age was 34 years (interquartile range (IQR): 27 - 40 years). The majority of the study population (75%; n = 6,841) were at most 40 years old. There were significantly more male blood donors (77.3%; n = 7,060) than female blood donors (22.7%; n = 2,066). The difference between the two gender proportions was statistically significant (p < 0.0001) at risk α = 5%. The male/female gender ratio was 3:4. The seroprevalence of HIV, HBV, HCV and Treponema pallidum was estimated at 2.6% (n = 237), 4.7% (n = 429), 3.3% (n = 297) and 0.4% (n = 33), respectively. A total of 927 (10.16%) donors were infected with at least one agent transmissible by blood transfusion. CONCLUSIONS: The present surveillance proves that infectious transfusion safety in Kinshasa is still very low.

Effect of vessel curvature on Doppler derived velocity profiles and fluid flow.

Side-branches and curvatures in the arterial tree yield deviations from the axial oriented velocity. Velocity or volume flow estimates based on the assumption that flow is axially oriented are of limited value at these sites. This article evaluates information obtainable by using a multigate Doppler ultrasound (US) instrument used with curved phantoms, which resemble the human coronary arteries. The comparison of experimental velocity data with data provided by an accurate computational fluid dynamics (CFD) method shows differences in the range of 4 to 11% for four curvatures with different radii. Multigate data are also used to estimate the volume flow in the curved segments at different experimental conditions. An error lower than 15% is obtained, to be compared with a 24% error obtained by assuming a parabolic velocity profile. In particular, it is shown that the residual error is not related to the small deviation of the velocity vectors from the axial direction due to the presence of secondary velocity components, which are found to be of magnitude less than 10% with respect to the axial velocity component.

A novel ultrasound instrument for investigation of arterial mechanics.

The study of arterial mechanics concerns functional characteristics depending on wall elasticity and flow profile. Wall elasticity can be investigated through the estimation of parameters like the arterial distensibility, which is of high clinical interest because of its known correlation not only with the advanced atherosclerotic disease, but also with aging and major risk factors for cardiovascular disease. The flow velocity profile is also clinically relevant, because it modulates endothelial function and can be responsible for the development and distribution of atherosclerotic plaques. A clinically relevant variable extracted from the blood velocity profile is the wall shear rate (WSR), which represents the spatial velocity gradient near the vessel wall. This paper describes an integrated ultrasound system, capable of detecting both the velocity profile and the wall movements in human arteries. It basically consists of a PC add-on board including a single high-speed digital signal processor. This is dedicated to the analysis of echo-signals backscattered from 128 range cells located along the axis of the interrogating ultrasound (US) beam. Echoes generated from the walls (characterized by high amplitudes and low Doppler frequencies) and from red blood cells (characterized by low amplitudes and relatively high Doppler frequencies) are independently processed in real-time. Wall velocity is detected through the autocorrelation algorithm, while blood velocity is investigated through a complete spectral analysis of all signals backscattered by erythrocytes and WSR is extracted from the estimated velocity profile. Preliminary applications of the new system, including the simultaneous analysis of blood flow and arterial wall movement in healthy volunteers and in a diseased patient, are discussed, and first results are presented.