The Two Measurement Principles Used by the STA Compact

This video covers the two methodologies used for making a measurement on the STA Compact.

A Transcription of The Two Measurement Principle Used by the STA Compact

Welcome to BioMedBuddy. Today we are going to cover the two methodologies used for making a measurement on the STA compact. First methodology is for clotting measurements. The second methodology is photometric measurements. (Screen change, :18)

The detection system for clotting time assays, on the STA compact, is based on the increase of viscosity of the plasma being tested. This increase of viscosity is measured by the motion of a stainless steel ball that is in the cuvette. (Drive Coils, highlighted in yellow, :36)The constant pendulum swing is created by an electromagnetic field, and it is applied alternately on opposite sides of the cuvette, by two coils.

The energy of that field can be varied, depending on the test being performed. As an example, for a weak clot, like for fibrinogen, and a normal clot, which would be all others.

There are two coils. One coil moves the ball to the left, and the other coil brings the ball to the right. (Receiving Transmitting Coils, highlighted in yellow, 1:10) When the ball slows down, the other two coils monitor that movement, and when the viscosity of the sample stops the ball from moving, you have a clotting time. As simple and easy as that.

All measurements are done on the measurement block. Positions 1 through 4. (“PTT-74.6”, highlighted in yellow, 1:31) When needle three comes down, it starts the clock running for your clotting test.

(Screen overlay displayed in yellow, 1:40) The second methodology is for photometric measurements. Again, the measurements are taken on the measurement block, positions 1 through 4, the front 4. (Flashing purple and yellow detail added to screen overlay, 1:55-3:25)A light from the optical module goes through some light pipes, through the cuvette, and is received on the other end, and goes to the photometric measurement board. There are two frequencies being used; 405 and 550 nanometers. A reference fiber comes directly from the optical module to the photometric measurement board, which is a means of eliminating incandescent light.

To make this simple, the optical module has a motor in it, and a light, and a filter. The filter is moved back and forth, or around, depending on the style of optical module in the unit. Most of them have a round filter wheel, at this point. The light goes through the filter, goes through four optical fibers, one to each channel on the measurement block, and a fifth fiber, which is the reference fiber. Which goes directly to the photometric measurement board.

Once those fiber optic cables reach the measurement wells, each cable goes through the cuvette, through the sample, and they're received on the other end. So, you have four fiber optic cables which go to the photometric boards from the measurement block. From there, the photometric measurement board goes to the CPU measurement board, out to the main CPU. Thus, you get your display of your test results.

Thank you very much for attending this session of the BioMedBuddy training, on the STA compact.