Shares of Affymetrix ( AFFX) were among the worst-performing health-related stocks Friday, falling 19% after the company posted second-quarter results that fell short of expectations and warned that third-quarter results would be below forecasts as well.

The biotech company reported earnings of $7.8 million, or 12 cents a share, on total sales of $84.1 million. Analysts polled by Thomson First Call were expecting earnings of 17 cents a share on sales of $88.1 million. A year ago the company earned $7 million, or 11 cents a share, on sales of $79.8 million.

Looking ahead, Affymetrix forecast a third-quarter loss of 6 cents a share on sales of $95 million. The earnings forecast includes charges of $17.5 million, or 27 cents a share, but excludes non-cash amortization of about $1 million, or 2 cents a share. Analysts had been expecting earnings of 29 cents a share on sales of $101.7 million. Shares were trading down $10.83 to $46.16.

Manor Care ( HCR) rose modestly after the company reported second-quarter earnings that beat forecasts. The operator of nursing homes reported earnings of $37.9 million, or 43 cents a share, on sales of $833.8 million. Excluding items, the company would have earned 48 cents a share. Analysts were expecting earnings of 46 cents a share on sales of $828.8 million. A year ago the company earned $40.1 million, or 45 cents a share, on sales of $799.1 million. In addition to earnings, Manor Care said its board has authorized an additional $300 million for stock repurchases. At the end of the second quarter, the company about $44 million remaining under its previously approved buyback plan. Shares were trading up 5 cents to $36.55.

Shares of Beckman Coulter ( BEC) fell 15% after the maker of testing instruments posted second-quarter earnings that fell well below expectations and slashed its 2005 guidance. The company reported earnings of $47.7 million, or 73 cents a share, on sales of $618.8 million. Excluding items, the company would have posted earnings of $51.9 million, or 80 cents a share. Analysts were expecting earnings of 92 cents a share on sales of $641.5 million. A year ago the company earned $58.3 million, or 88 cents a share, on sales of $597.3 million.

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