the oral administration of metallic colloids, in particular colloidal silver protein, has been reported to have toxic effects (2 the oral administration of metallic colloids, in particular colloidal silver protein, has been reported to have toxic effects (2). Despite this, dozens of companies sell metal colloids as nutritional supplements. Many metal colloids have been rebranded as “nano” compounds to further intensify the public’s interest in their utility. Although clinical concern about the use of colloidal metallic compounds is longstanding, their effects on laboratory tests have not been investigated. These particles are of particular concern because their small size allows high oral bioavailability, accumulation within the blood, and excretion through the kidneys (5). We were interested to know whether metal colloids might cause interference in clinical chemistry tests of blood and urine. We tested 4 nutraceutical products: Mesogold, Mesosilver, Mesocopper, and Mesoplatinum [Purest Colloids, Inc.; daily recommended doses ranged from 50 to 150 μg (4)]. These were colloidal suspensions of nonionic metal with 1-to 10-nm diameter particles. The concentrations of copper, silver, platinum, and gold measured by National Medical Services, Inc. were 0.9, 21, 13, and 18 mg/L of each metal, respectively, whereas the manufacturer’s stated concentrations were 10, 20, 10, and 10 mg/L, respectively. We tested the mesometals (undiluted and as 1: 1 mixtures with saline or pooled serum) for interference in a range of automated assays on a Vitros® Model 950 AT: glucose, blood urea nitrogen, creatinine, ammonia, sodium, potassium, chloride, total CO2, amylase, lipase, calcium, magnesium, phosphate, cholesterol, triglycerides, uric acid, albumin, aspartate aminotransferase, alanine aminotransferase (ALT), lactate dehydrogenase (LD), creatine kinase, alkaline phosphatase,-glutamyl transpeptidase, conjugated bilirubin, and unconjugated bilirubin. We also tested various point-of-care methods: Quickvue® One Step hCG Urine (Quidel Corp.); Acceava® hCG Combo (ThermoBiostar); and Chemstrip® 10 S-UA (Roche Diagnostics). The concentrations tested were likely much higher than might be found clinically, and they were chosen to reveal any possible effects. We found no interferences (1: 1 sera: saline vs sera: mesometals) with the exception of LD (10%–20% lower) and ALT (13%–50% higher). Of note, assaying the mesometals directly showed consistently detectable LD (range, 129–182 U/L) and low ALT activities (17–21 U/L) for all metals tested.

We also tested mesometals [undiluted and as 1: 1 mixtures in control serum with added drugs (Lyphochek® Immunoassay Positive Control, Ethanol/Ammonia Control; Bio-Rad)] in Emit assays for lidocaine and amikacin, and for ethanol on the Hitachi 911, but we found no interference.