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Optical vs. Mechanical Clot Detection — Which one should I choose?Healthcare News | May 28, 2009
A variety of hemostasis systems are available for tests such as prothrombin time (PT), activated partial thromboplastin time (APTT) and fibrinogen (FIB). There are two distinct technological methods for clot detection: Optical and mechanical. In September, 2008, the largest study to date was published, comparing clot detection methods1. The study’s goals were: “…to determine the rates at which optical and mechanical detection of coagulation fail to yield a measurable end point in routine patient samples in a high-volume hospital setting [and] whether mechanical or optical detection provides more reliable results as judged by the tilt tube method using suboptimal samples.”
High degree of correlation
The degree of visually observable interference in study samples was characterized according to a “Sample Integrity Chart,” providing semi-quantitative and qualitative grading based on color and cloudiness. Of the samples tested, some 26.5% had visible interferences caused by hemolysis, lipemia (turbidity) and/or icterus. The results showed that photo-optical and electro-mechanical detection systems were highly correlated (r-squared values ≥ 0.96 for all assays). Correlation between the two detection systems was maintained even when measuring turbid samples (r-squared values ≥ 0.98 for all assays). The rate at which both photo-optical and mechanical testing methods failed to yield a measurable end point was less than 1.2%.
The study’s conclusion
The study showed that mechanical clot detection and photo-optical clot detection are statistically equivalent, disputing the misconception that mechanical clot detection is superior to photo-optical clot detection.
“The results indicate that turbidity has no significant effect on photo-optical detection as compared to mechanical detection. Results obtained by the photo-optical detection system are as reliable and statistically equivalent as those obtained using the mechanical detection system.”
Visualizing Abnormal Clot Formation
Siemens offers a wide range of photo-optical hemostasis systems. The Sysmex® CA-family and BCS® XP System utilize the power of the wavelength spectrum to minimize the interfering effects of hemolysis, icterus, and lipemia. Features of photo-optical clot detection over mechanical detection systems:
- Entire course of clot formation is recorded
- Reaction changes can be easily identified
- There are sophisticated software algorithms
- Clot curves show complete clot signature image
Hemostasis Portfolio
1. Bai et al. Comparison of optical and mechanical clot detection for routine coagulation testing in a large volume clinical laboratory. Blood Coagul Fibrinolysis. 2008; 19:569-576
(Study was sponsored by Siemens Healthcare Diagnostics)
