Which of the following may be a sampling source of error for an automated instrument?

• A. Short sample
• B. Air bubble in bottom of sample cup
• C. Fibrin clot in sample probe
• D. All the above

Answer: (D)

Sampling errors in automated instruments come from anything that interferes with how the sample is physically drawn, transported, or presented to the detector. Each of these situations can disrupt that process and lead to incorrect or unreliable results.

A short sample means there isn’t enough volume for the instrument to aspirate and analyze properly. The instrument may pull in an inconsistent amount of liquid, may aspirate air, or may fail to reach the required probe position, all of which can skew results or trigger error conditions.

An air bubble at the bottom of the sample cup can be pulled into the probe during aspiration. That air compresses differently from liquid, can interrupt continuous flow, and often results in incomplete aspiration or stray readings, compromising accuracy.

A fibrin clot in the sample probe can physically block or constrict the path the sample must travel. This can slow or stop aspiration, cause incomplete sampling, or force the instrument to compensate in ways that produce erroneous measurements or alarms.

Because any of these issues can occur and each affects how the sample is measured, all of the above may be sources of sampling error.