Optimizing the Limit of Detection of Waveguide-Based Interferometric Biosensor Devices

Waveguide-based photonic sensors provide a unique combination of high sensitivity, compact size and label-free, multiplexed operation. Interferometric configurations furthermore enable a simple, fixed-wavelength read-out making them particularly suitable for low-cost diagnostic and monitoring devices. Their limit of detection, i.e., the lowest analyte concentration that can be reliably observed, mainly depends on the sensors response to small refractive index changes, and the noise in the read-out system. While enhancements in the sensors response have been extensively studied, noise optimization has received much less attention. Here we show that order-of-magnitude enhancements in the limit of detection can be achieved through systematic noise reduction, and demonstrate a limit of detection of ∼10−8RIU with a silicon nitride sensor operating at telecom wavelengths.

[Clinical validation of minimally invasive evaluation of systolic function]

BACKGROUND AND OBJECTIVE

Pulse contour continuous cardiac output (PiCCO) monitoring by means of transpulmonary thermodilution provides 2 indices of systolic function: the cardiac function index and the global ejection fraction. Our aim was to compare these 2 PiCCO indices to the left-ventricular ejection fraction obtained by transthoracic echocardiography.

MATERIAL AND METHODS

This was a prospective clinical study of 35 adult patients in the critical care unit of a university hospital. Each patient provided his or her own control data. Patients with marked changes in regional segment contractility or nonsinus rhythm were excluded. We collected patient variables, reason for admission to the critical care unit, the Acute Physiology and Chronic Health Evaluation II score, the reason for hemodynamic monitoring, and the infusion of vasoactive drugs at the time of the procedure.

RESULTS

Statistically significant correlations were found between the left-ventricular ejection fraction and the global ejection fraction (r=0.79, P<.001) and the cardiac function index (r=0.66, P<.001). The mean (SD) difference between the left-ventricular ejection fraction and the global ejection fraction and the cardiac function index were 1.05% (10.2%) (range, 19.0% to 29.1%) and 0.001% (12.4%) (range, -24.3% to 24.3%), respectively. For predicting a left-ventricular ejection fraction of less than 40%, the area under the curve was 0.879 for the global ejection fraction and 0.805 for the cardiac function index of A global ejection fraction less than 13.5% and a cardiac function index less than 3.15 min(-1) predicted a left-ventricular ejection fraction less than 40% with sensitivities of 97% and 96% and specificities of 85% and 77%, respectively.

CONCLUSIONS

In patients without marked changes in regional segment contractility, the global ejection fraction and the cardiac function index calculated by the PiCCO monitor offer a reliable and simple way to assess left-ventricular systolic function. Low values for these indicators suggest the need for echocardiographic assessment of left- and right-ventricular function.

[Spanish extrahospitalary hemodialysis centers survey]

BACKGROUND

Many guides and scientific recommendations about hemodialysis (HD) treatment have been developed. However, its impact and application is unknown. The aim of this study is to describe how Spanish Extrahospitalary Hemodialysis Centers work.

METHODS

A transversal, descriptive study was conducted by means of a survey. An 83-items questionnaire tackled different aspects involving patients and HD characteristics, Dialysis Unit organization and anemia management.

RESULTS

One hundred surveys were distributed and 91% were answered, corresponding to 6599 patients (M 4015/F 2584). Fifteen % were younger of 50 years and 45.2% older of 70 years. Seventy seven % had arteriovenous fistulas, 8.1% had polytetrafluoroethylene grafts and 14.8% had catheters. The mean number of patients per center was 72.3 (11-212). Seventy eight % were divided in 3 shifts, with a mean relationship of 38.9 patients/physician, 4.7 patients/nurse and 9 patients/auxiliary personnel. HD characteristics were: 60.1% of the HD sessions were longer than 4 hours, 97.2% were on a 3 days/week schedule; 95.4% used a conventional technique; 49.1% were performed with high-flux membranes, 89.6% with synthetic membranes, and 11.7% used Qb higher than 400 mL/min: On the other hand, 8.8% of the patients were HVC +, 0.68% were AgHBs +, and 0.09 were HIV +. There were HCV + patients in 79% of Dialysis Units, 50% of them with complete isolation, while patients with hepatitis B were attended in 13.8%, and VIH + in 3.4% of the Units, the latter always with complete isolation. Water treatment was done with simple osmosis in 46.6% of the cases, with water collection in 86.8% with pyrogen filter in the monitors in 48.9%. Surveillance of the controls was performed by the physician in 94.3% of the cases, and by technicians or nurses in the rest. Mean Hb was 11.9(1.4) g/dL, being higher of 11 g/dL in 80.2% of the patients. Ferritin higher than 100 microg/L was found in 92.4% and transferrin saturation higher than 20% in 81.9% of patients. The percentage treated with erithropoyetic stimulant agents was 90.6%.

CONCLUSIONS

All information collected is relevant in order to know what is done and how to improve it.. It will be useful to evaluate the impact of the publication of the new Guides of HD Centers of SEN on medical practice in this area.

Phalangeal Bone Ultrasound and Its Possible Correlation with Nutrient in an Area of High Protein Intake

AIMS

The influence of eating habits on bone mass is a controversial topic. We have use ultrasound to search for the relationships between nutrients and bone density.

METHODS

A total of 228 women (mean age 48.9 +/- 13.7 years) were studied, and divided according to their gonadal status (pre-, peri- and postmenopausal women). The dietary intake was recorded for 7 days, and their bone mass was measured by phalangeal amplitude-dependent speed of sound (Ad-SOS). ANOVA was made to examine the differences according to gonadal status. To determine the possible correlation between Ad-SOS and nutrient intake, partial correlations, adjusted for important confounding variables, were done.

RESULTS

With partial correlations, there was no correlation of Ad-SOS with the nutrients studied here.

CONCLUSION

We find no correlation of bone mass as measured by Ad-SOS with the most common nutrients and trace minerals, either for the participants as a whole or according to gonadal status.

Influence of vitamin D administration on bone ultrasound measurements in patients on anticonvulsant therapy

BACKGROUND

The objective of the study was to evaluate bone mass status (as measured by bone ultrasound) in patients on anticonvulsant therapy, and the influence that Vitamin D administration exerts over it.

MATERIALS AND METHODS

We measured and compared the basal serum levels of 25(OH)D3, parathyroid hormone (PTH), and phalangeal bone ultrasound (Ad-SOS), in 30 adult patients who were taking anticonvulsant drugs, with a control group of similar age and sex. We then gave the patients a large oral dose of 3 mg (120.000 UI) of 25(OH)D3, and repeated the measurements after one month.

RESULTS

Basal 25(OH)D3 and Ad-SOS values were significantly lower, and PTH values significantly higher (P< 0.0001 in all), in the patient group. The low Ad-SOS values for the patients were independent of the treatment, but directly related to basal 25(OH)D3 levels (r = 0.45, P<0.01). There was a negative association between PTH and 25(OH)D3 (r = -0.64, P<0.0001), and no correlation between PTH y Ad-SOS (r = -0.20, p NS). After ingestion of the large dose of the vitamin D, the patient group registered a significant (P<0.0001) increase in 25(OH)D3 levels, their Ad-SOS values increased (P<0.0001) nearly to the mean basal value of the control group, and PTH decreased significantly (P<0.0001).

CONCLUSIONS

These findings justify the need to assure adequate vitamin D intake in patients being treated with anticonvulsants, independently of the treatment, age, sex, and activity status, in order to prevent osteomalacia.