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Current Point-of-Care Diagnostics

 

 

The Diagnostic Box envisioned by UW bioengineer Paul Yager would be a pocket-size laboratory able to tell physicians within minutes whether a patient had contracted various life-threatening diseases endemic to underdeveloped regions. Yager and his group recently received $15 million to develop the technology.

Source: www.washington.edu/.../article_gadget.html

 

 

Due to the fact that most of the clinical laboratory errors occur during the preanalytical phase, meaning wrong labels on samples taken or loss of sample altogether, performing diagnostic analysis on site would prove a valuable method of choice for error reduction. Using Point-of-Care technology at one location will virtually eliminate all transportation problems and reduce the amount of people involved between blood sampling and data interpretation. Products such as glucose monitoring devices have already resulted in a dramatic improvement in diabetic patient care and quality of life, while reducing the taxing demands such frequent tests would have on clinical laboratories. The primary limitation with POCT in its current state is the lack of performance analysis to compare its accuracy with that of the clinical setting. In addition, the current state of POCT technology cannot analyze as wide of a variety of parameters as can be performed in the laboratory. In general, one device can test anywhere from 1 to 20 parameters but to do so may require repeat tests with five or more disposable lab on a chip cartridges. Currently, it is difficult to compare between POCT and the central laboratory making it difficult to determine if any technology or approach is a significant improvement over the other.

 

 

Current Limitations

1.                  Requires frequent calibration

2.                  Unproven track record

3.                  Long term storage problematic

4.                  Surviving harsh conditions without failure

5.                  Contamination

6.                  Limited diagnostic ability for each device

7.                  Lack of technology

8.                  Not yet a complete walk away technology (no personnel supervision)

9.                  Currently a higher cost than most clinical laboratory tests

 

 

 

Possible Advantages

1.                  Direct point of care technology avoids long sample transport

2.                  Faster medical decisions

3.                  Portable

4.                  Disposable technology

5.                  Potential for reduced cost

6.                  Improved fluid handling

7.                  Sample size reduction

8.                  Hands free

9.                  Third world

10.             Biodefense applications

11.             Personal care

12.             Emergency response equipment

 

 

 

Analysis techniques

Depending on the sample to be analyzed and the target analytes or biomarkers, there may exist a variety of analysis and measurement techniques as shown in table 3 below.

 

Table 3 Analytical principles used for the determination of analytes

Principle of analysis

Principles of measurement

Examples

1) Light scatter

Laser-induced forward scatter

Blood cell count

2) Electrodes

Voltage changes

Electrolytes

3) Chemical

Optical/transmission

Creatinine

4) Biochemical assay

Optical/transmission

GOT,LDH, CK etc.

5) Antibody-based assays

Optical/light scattering etc.

Hormones, drugs

6) Electrochemical based assays

Electric current

Catecholamines and degradation products

7) Separation by charge

Electrophoresis/HPLC

Plasma proteins, Hbs

8) Trace elements

Atomic absorption

Se, Zn, etc.

(Source: Schleicher, 2006)

 

 

 

A typical Point-of-Care analysis process

1.                  Insert sample in microfluidic lab on a chip

2.                  Place lab-on-a-chip cartridge in analyzing instrument

3.                  Press start and wait 5-10 minutes for printout of results

 

Source: http://www.abaxis.com/medical/piccolo_operation.html

 

 

 

New enabling technology

Technologies and processes that will further enable POC technology are summarized as follows

1.                  Exploiting scaling phenomena to discover new detection schemes for future applications

2.                  Disposables interfacing with a non disposable housing/analyzer

3.                  Taking large pieces of equipment and shrinking them down

4.                  Reducing sample size and reagents used

5.                  Improving detection sensitivity

6.                  Reducing processing time

7.                  Mass parallel processing

 

 

Examples technologies

What was once a large bulky piece of equipment with large power consumptions has now been miniaturized into a portable, laptop sized ultrasound imaging device for emergency response personnel and third world countries.

 

Source: http://www.idsa.org/IDEA2006/galleries/idea/idea2006/award_details.asp?id=83&cat=9

 

 

 

 

On this disk we can perform over 24 different tests in a single process on a disposable disc the size of a CD. All fluid transport is driven by capillary and centrifugal forces to enable parallel processing of data on a single run.

 

Source: www.bioloc.net/cd-elisa-unique.htm

 

 

 

 

New technology and detection schemes allow for the processing and detection of multiple analytes or pathogens within a single test using an array based immunoassay. Here an electrochemical sensor can detect the byproducts of different catalysts functionalized by three different types of antibodies. In this fashion, multiple targets can be detected on a single test run.

 

(Source: Wang, 2006)

 

 

 

 

Here they exploit the scaling effects of a magnetic field to develop a Hall Effect sensor combined with a sandwich immunoassay technique.

 

 

Source: www.coe.berkeley.edu/labnotes/1003/boser.html

 

 

 

A recent POCT Technology Review

For a thorough analysis and review of the current point of care technology, refer to the link below.

http://www.prwebdirect.com/releases/2006/5/prweb387007.php

 

 

 

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