As of July 2020, we have completed some useful testing on a number of GS samples. This should help take some of the mystery out of what folks are putting in their cats. The testing includes a mix of current GS brands and some older brands that were suspected of causing problems. The actual testing was performed by an anonymous contributor at a nearby prestigious university.

The full report is here 

The raw data is here

We want to stress that this testing data should not be used as the sole means for selecting a brand. Much higher priority should be given to clinical results of a brand used to treat a large number of cats over the full 84 days of treatment and 84 dyas of post treatment observation. Further, the clinical results should include “tough” cases such as Ocular and neuro forms of FIP. At this time, we feel that Capella and Brava meet this criteria.

The full report and some of what follows is highly technical so if you want to skip all that, you can scroll down where we summarize some of the results

Test Method: There are various possible methods that can be used to test GS samples. The data discussed here was acquired with an instrument called a Nanodrop Spectrophotometer. A Nanodrop passes light through a sample and measures the absorption of the light as a function of wavelength (color). The Nanodrop device is really designed to analyze RNA samples which have a characteristic absorption band in the UV (ultraviolet) which peaks near 260nm (nanometers). Since GS is able to bind to RNA in the virus, it turns out that GS has an absorption profile that is similar to RNA in the same range of wavelengths. While RNA has a single absorption band near 260nm, GS has two absorption bands: one near 240nm and another one near 300nm. We believe this method is very good for measuring concentration and also provides some data on purity. The gold standard method for purity would be High Pressure Liquid Chromatography with Mass Spectroscopy (HPLC-MS). This type of machine is very expensive and more easily damaged. Since an HPLC-MS was not readily available, we have done the best we could with the Nanodrop.

The Nanodrop is an very sensitive instrument. In order to get GS samples in a good range for measurement, they had to be diluted at 1:120. Data was also acquired at half that dilution (1:60). To determine actual concentration, we prepared Standard samples at various dilutions using GS powder provided by one of the more trusted GS brands. The concentrations are quoted relative to 15mg/ml but the actual data shown here was taken at 1:120 dilution.

Capella and Brava: The plot below shows three data sets: the 15mg/ml standard, a recent random sample from a Capella shipment, and a recent random sample from a Brava shipment. The higher the peak, the more light was absorbed indicating higher concentration. From details of the shape of the curve, we can infer some information about purity. We will leave the purity discussion for the complete report. The surprising result we see here is that the actual concentrations for Capella and Brava are higher than the quoted 15mg/ml. This result is of course based on the accuracy of the Standard preparation. Since the Standards were prepared and tested three times, we have high confidence that these results are correct to within 5%. The data suggests that both Capella and Brava are around 18mg/ml and Brava has slightly more GS than Capella.

Hero: Hero is a brand that is widely sold in other groups. This sample from a “white cap” bottle is claimed to have a higher GS concentration (than the 15mg/ml standard) of 16.5 mg/ml. We can see in plot below that the hero data very closely overlays the data for the 15mg/ml Standard. Clearly it is not 16.5mg/ml. This is the what people mean when they caution owners that want to treat their cats that the available products are black market.