* SPDR Gold Trust GLD, the world's largest gold-backed exchange-traded fund, said its holdings fell 0.16% to 924.25 tonnes on Tuesday from 925.70 tonnes on Monday. April 19 (Reuters) - Gold prices edged higher on Wednesday, helped by a softer U.S. dollar, while traders assessed prospects of the Federal Reserve raising interest rates just once more in May before pausing. * Gold is considered a hedge against inflation and economic uncertainties, but higher interest rates dim the non-yielding asset's appeal.