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The False Positive Dilemma

Blood testingFalse Positives when Testing Blood aren’t Avoidable

Although movies show scientists in lab coats testing strange samples using pipettes and syringes, the reality is far different. Oftentimes, a mechanized chemistry analyzer conducts hospital blood tests, including blood alcohol tests. However, this does not rule out the potential for false positives, as outlined below.

What is a Clinical Chemistry Analyzer?
As the name suggests, a clinical chemistry analyzer is a piece of equipment that determines the chemical makeup of certain substances such as blood, urine or other bodily fluids. Chemistry analyzers are used to monitor diseases, tests for certain metabolites in the sample, and, very importantly, determine whether or not drugs are present in the sample.

How Does a Clinical Chemistry Analyzer Work?
Simply put, clinical chemistry analyzers run assays on medical samples in order to measure the constituents and concentration of a predetermined substance referred to as an analyte.

In order to do so, a clinician will load a sample into the chemistry analyzer. The machine will then measure out a specific aliquot of the sample, and release it into the reaction vessel. Reagents are then added to the sample and, if necessary, it will be allowed to incubate for a certain period of time. Different methods can then be used to determine the chemistry of the sample, such as ion-selective electrode testing or photometric testing to measure absorbance. Once the assay is completed, the clinical chemistry analyzer will provide a detailed report on the constituents and chemical concentrations of the sample.

Which Clinical Chemistry Analyzer Should You Choose?
Clinical chemistry analyzers come in all shapes and sizes, including small, compact devices that can fit onto a desk top and large, hospital-grade analyzers that are larger than a single bed. Regardless of size and abilities, there is a growing demand for any type of analyzer to provide accurate results as quickly as possible with as little cost. The need to analyze bodily fluids, especially blood, to aid legal cases has become increasingly popular.

When it comes down to it, there are two main types of clinical chemistry analyzers; ones built for small clinics and laboratories, and ones built for large laboratories and hospitals. Here is a brief outline of two of the best chemistry analyzers on the market.

VITROS® 350 Chemistry System: this compact, bedside analyzer can generate up to 300 results in one hour, depending on the type of analysis run. It helps meet increased demand for disease-focused panels by delivering almost immediate results for emergency or routine tests, and requires fewer dilutions, repeats and redraws than the usual liquid systems.

VITROS® 5600 Integrated System: this large-scale, integrated system allows more than 100 assays on board at once, thus decreasing processing time while simultaneously increasing efficiency by reducing the for non-renewable resources by using a waterless system.

Problems and False Positives
Although the purpose of using technology and machines to replace physical testing is to minimize the potential for human error, the use of clinical chemistry analyzers does not mean that mistakes cannot happen. In a hospital environment where hundreds of assays are lined up to be analyzed, there is still the possibility for contamination to occur. Moreover, the use of chemistry analyzers does not rule out the likelihood of false positives occurring, which can be caused by many different variables. For example, someone who has eaten a poppy seed muffin and is then tested for opium may still test positive when a clinical chemistry analyzer is used to examine his or her blood, as the analyzer will still detect traces of opium. These types of false-positives can occur with any substance, including alcohol or prescription medications. For these reasons a forensic toxicologist should always be employed to investigate the results produced in order to ascertain whether or not the clinical chemistry analyzer has detected a false positive.

If you feel that you have been wrongfully accused because of a false positive, do not hesitate to contact Okorie Okorocha to help scrutinize the results of a chemistry analyzer.

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