A sampling system includes an aspiration line having an aspiration pump in series with an aspiration probe. A pressure transducer 0-100 psi (26PCFFG6G) is used after the sampling probe and connected to the pump via a pipette. When a test sample is aspirated the valve is in the first valve position and the transducer provides output voltage readings at predetermined time intervals during the aspiration cycle that correspond to the vacuum level in the aspiration probe during aspiration. A microprocessor is connected to the pressure transducer compares the new/test aspirated sample output voltage to the one already stored in the memory for unclotted sample serum. When the transducer output voltage for the test sample differs from the reference voltage level by an amount greater than two/three standard deviations of the reference voltage, it can be determined that the test sample aspiration was impeded by a blood clot and would not provide a reliable evaluation at the sampling system reading station.

The discrepant test sample aspiration is thus unacceptable for test purposes and is kept isolated from the analytical line by automatically changing the valve position to prevent it from reaching the reading station and dispensing the clotted sample to clean the sampling probe tip.

If the difference between the test sample aspirations output voltage level and the reference voltage level is less than two/three standard deviations of the reference voltage level, the test sample is considered acceptable for test purposes.