1. Bocci, V, (1963). Nature (Lond.), 197, 491.
2. Smithies, 0. (1955). Biochem. J., 61, 629.
3. Letters to the Editor suitable and the modified method (cetylpyridinium chloride citrate turbidity) is as follows: For the blank 1 ml of filtered urine is added to 1 ml of a citrate buffer (pH 4 8) containing 9-68 g of citric acid per litre and 15-88 g of trisodium citrate per litre,1959
4. critical time dependence of the method of Manley and Hawksworth,1966
5. Cetylpyridinium chloride precipitable uronic acid (a useful guide to glycosaminoglycan concentration although it will not reflect the amount of kerato sulphate or mucoprotein coprecipitated) was isolated as described by Di Ferrante (1967), assayed by the method of Bitter and Muir (1962), and compared with the cetylpyridinium chloride turbidity test described here. There was good correlation between cetylpyridinium chloride precipitable uronic acid and both screening tests (Table I) but correlation was better for the modified method