Apollo Health Street, the BPO arm of Chennai-based Apollo Hospitals, is planning an Initial Public Offering (IPO). The company may dilute 15 per cent of equity stake to raise about $70–80 million.The IPO is expected to hit the markets by the first quarter of year 2008.Analysts see the valuation of Apollo Health Street could be anything between $470-500 million, however, management prefers to maintain silence.