First, cash flow. Our cash flow remained strong. Free cash flow for the trailing 12 months ended June 30, 2012, were $749.5 million, excluding the Hunter Labs settlement. We remain pleased with our cash collections. DSO was 47 days at the end of June, a decrease of 1 day sequentially and an increase of 1 day year-over-year. During the quarter, we maintained our bad debt rate of 4.4%.
Second, revenue growth. Revenue increased 1.4% year-over-year in the second quarter. During the quarter, revenue per requisition increased 1.5% year-over-year. Total company volume was essentially flat year-over-year during the second quarter. Esoteric volume increased approximately 1.3% in the quarter.
Third, margin. For the second quarter, our adjusted operating income margin was 19.7% compared to 19.9% in the second quarter of 2011. The decline in adjusted operating income margin is due to a 30-basis-point drag from recent acquisitions that we've not fully integrated.
Fourth, liquidity. We remain well capitalized. At the end of June, we had cash of $124.4 million and $510 million available under our credit facility. During the second quarter, we repurchased $130.3 million of stock, representing 1.5 million shares. Year-to-date, we repurchased 2.9 million shares for $252.6 million. At the end of June, $332 million of repurchase authorization remained under our share repurchase program. This morning, we updated our 2012 the financial guidance. We expect revenue growth of 2% to 3%; adjusted EPS, excluding amortization, in the range of $6.80 to $7, excluding the impact of any share repurchase activity after June 30, 2012; operating cash flow of approximately $950 million; and capital expenditures of approximately $155 million.I'll now turn the call over to Dave. David P. King Thank you, Brad. We are pleased with our performance, given that we continue to face a very difficult environment for volume growth. During the quarter, we grew earnings per share by nearly 8% year-over-year. We continued to integrate our recent acquisitions and focus on expense control, lowering our selling, general and administrative expenses as a percentage of revenue by 90 basis points year-over-year, adjusted for the Hunter Labs settlement and Orchid legal expenses in 2011. And we extended our contract with WellPoint on a multi-year basis, stable pricing and continue the exclusivity in our key markets. Read the rest of this transcript for free on seekingalpha.com