(1) No constant relation has as yet been established between the uric acid content of the blood and acute attacks of gout.
(2) No variations in the same apparently herald or accompany typical acute paroxysms.
(3) Attacks may occur with a sub-normal uric acid blood content.
(4) The tissues of gouty subjects apparently possess an enhanced binding capacity in respect of uric acid.
(5) Given impaired renal excretion in gouty subjects, the uric acid content of the joint fluid rises markedly, exceeding that of the blood.
Discussion of the Foregoing Data
While the researches of the past decade have proved distinctly encouraging, yet we must not blind ourselves to the fact that the foregoing findings, and alike our deductions therefrom, are largely provisional; for we stand in grave danger of over-emphasising the significance of the results forthcoming from the investigation of isolated samples of blood from different individuals. The recorded estimates of the uric acid content of the blood in strictly normal persons are all too few, the findings in diseased subjects too conflicting, to warrant dogmatic inferences, wide generalisations. In truth, the problem is by no means as simple as may at first sight appear, and this but a slight digression will suffice to make clear.
The Significance of Uricæmia.—It is generally maintained that the blood content of uric acid in gout is above normal. Yet the excretion of uric acid, save during acute attacks, rests within physiological limits. Again, à propos of our claim that the blood is surcharged therewith, we have the awkward fact, as yet inexplicable on chemical or physico-chemical grounds, that the blood-stream can hold in suspension far more uric acid than has ever yet been met with in gout, according to Bechhold and Ziegler no less than 50 mg. of uric acid per 100 c.c. of blood serum before deposition tends to occur. On the other hand, urates are less soluble therein, not exceeding 2·5 mg. per 100 c.c. How remote from the limit of saturation the highest figures observed in gout! What a large margin of solubility is still available!
Again, the uric acid blood content in gout is far less than was formerly thought. Only by a few milligrams does it transcend that found in normal individuals. Can this slight disparity have such profound potentialities as to determine the incidence or not of gout? and this with the saturation point still so remote. The urates, too, being practically non-toxic, how difficult to conceive that the almost trivial excess of the uric acid blood content over the normal is adequate to produce the fulminant and dramatic phenomena of acute gout.
Again, though we speak of uricæmia as a dominant characteristic of gout, we are uncertain whether the alleged increase in the uric acid content of the blood is real or merely apparent. We can, it is true, extract uric acid and urates from the blood-stream, but it does not necessarily follow that it is as such that they circulate in vivo. We need walk circumspectly here for, despite the most modern methods of blood analysis, we are still ignorant as to the exact form in which uric acid exists in the blood-stream; whether the purins of the food appear in the blood-stream as sodium monourate, or in organic fusion. Accordingly, in the interests of progress, it were well to bear in mind the pitfalls that beset uric acid estimation, the insufficiently eclectic capacity of even the most modern tests, and to consideration of these more chastening aspects we now proceed.