Which of the following specimens require chilling?

Specimens that require chilling are typically those that are sensitive to temperature changes and may undergo degradation or alterations if not properly maintained. The correct answer includes ammonia, lactic acid, and arterial blood gas, all of which are known to require chilling to preserve their stability until they can be processed.

Ammonia, for instance, is subject to rapid metabolism by cells in the specimen; therefore, chilling the sample helps minimize this metabolic change, ensuring accurate results. Lactic acid levels are also sensitive and can be affected by temperature, as altitudes in lactic acid can differ due to cellular metabolism occurring after the blood collection. Arterial blood gas specimens must be kept chilled to maintain the integrity of pH, pCO2, and pO2 measurements, as ambient temperature can affect gas solubility and readings.

The other listed combinations do not all include specimens that require chilling. For example, parathyroid hormone and blood glucose can be stored at room temperature under certain guidelines, meaning they do not necessitate chilling as part of the standard protocol.