A standardised protocol for the quantification of lactate dehydrogenase activity in saliva

The literature about salivary lactate dehydrogenase (LDH) activity shows different results, conditioned by the diversity of methods used for sampling, handling and analysis. Objetives: The aim of this study was to design a protocol for quantifying salivary lactate dehydrogenase activity. Methods: Whole saliva samples were collected from 100 healthy volunteers by chewing a roll of cotton. Lactate dehydrogenase activity determinations were made with the Cobas Mira Plus II® autoanalyser using the recommendations proposed by the International Federation of Clinical Chemistry (IFCC) and the French Society of Clinical Biology (SFBC). Samples were stored at room temperature (20–22 °C), in the refrigerator (4 °C) and freezer (−20 °C). The correction capacity of the autoanalyser was evaluated by making serial determinations in samples of saliva diluted in water. Results: The frozen samples, but not those stored in the refrigerator or at room temperature, showed an important degradation of lactate dehydrogenase activity. When the samples were diluted in water, the lactate dehydrogenase activity varied substantially with the International Federation of Clinical Chemistry method after correction, but not when using the French Society of Clinical Biology method. Conclusion: For salivary lactate dehydrogenase activity quantification we suggest that samples be stored at 4 °C and analyse with the French Society of Clinical Biology method.