Low levels of zinc contamination has been found in red top (RT), brown top (BT), and green top (GT) test tubes from a commonly used supplier. While the normal reference range for blood zinc concentration is 0.8-2.5 ppm, these tubes contain zinc concentrations as high as 3–6 ppm. Thus, use of these tubes could cause a normal bird to appear to have zinc toxicosis.

Microtainer™ brand tubes [either spun GTs with separator gel or spun serum separator tubes (SST)] or royal blue top Vacutainer™ tubes are preferred for measuring blood zinc concentrations. Please call the laboratory if you need some of these tubes.

Antech Diagnostics has recently introduced a new ELISA based assay for cryptococcal antigen. This replaces the former method and is reported either as negative, or as positive with a quantitative endpoint titer.

Although endogenous TSH levels should be elevated in primary hypothyroidism, this assay used alone has relatively poor predictive value of true hypothyroidism in the dog. This is in contrast to humans where endogenous TSH levels are very accurate in predicting thyroid function status.

Because of the significant (up to 40%) discordancy found with canine TSH testing (i.e. high in euthyroid dogs, and low or normal in hypothyroid dogs), Antech Diagnostics does not recommend using this test as a sole predictor of thyroid function in dogs, and accords less significance to the TSH result than to other thyroid analytes measured and the clinical status of the patient.

References: Nachreiner et al, AJVR 59: 951-955, 1998; Antech News, November 1998; Bruner et al, JAVMA 212: 1572-1575, 1998; Dodds, Proc AHVMA, pp. 77-79, 1999.