Updated from 2:31 p.m. EDT

Shares of Ciphergen Biosystems ( CIPH) were among the best-performing health and pharmaceutical stocks Tuesday, rising 31.6% after the company said it discovered a way to detect cancer earlier.

The company's ProteinChip technology was able to detect "human cancers of a microscopic size undetectable by any presently available diagnostic method," said the authors of the study. The findings were presented at the American Society for Hematology 46th annual meeting in San Diego today. The company said the technology "potentially may be used for early diagnosis of cancer allowing for earlier treatment." Shares traded up $1.05 to $4.37.

Discovery Labs ( DSCO) rose 20.5% after the company announced promising results from its ongoing Surfaxin phase II clinical trial. The company said that patients using Surfaxin, a drug used to treat acute respiration distress syndrome (ARDS), along with mechanical ventilation showed a 31% improvement in overall mortality versus those who only used mechanical ventilation. As of November 15, 2004, a total of 89 patients were enrolled in the trial and completed the 28-day study. Discovery Labs expects the phase II trial to be completed by the fourth quarter of 2005. Shares traded up $1.40 to $8.22.

Despite posting a third-quarter loss and warning that 2005 earnings results would be far below expectations, shares of Vistacare ( VSTA) rose 6.7% on Tuesday. The hospice services company posted a loss of $6.2 million, or 38 cents a share, on revenue of $48.7 million. The company said third-quarter results were hurt by increased costs associated with marketing staff recruiting, training and compensation, as well as with costs associated with additional legal, insurance, severance and lease termination expenses. Looking ahead, the company forecast 2005 earnings of 35 cents to 45 cents a share. Analysts polled by Thomson First Call had been expecting earnings of 61 cents a share. Shares traded up $1.02 to $16.22.

Alliance Imaging ( AIQ) fell 12.7% after the medical diagnostic services company warned that 2005 earnings would fall below expectations. The company expects earnings of 44 cents to 51 cents a share, below analysts' expectations of 52 cents a share. The company expects sales of $427 million to $437 million, below the one-analyst estimate of $450.1 million. Shares traded down $1.25 to $8.58.

Other health care volume movers included Pfizer ( PFE - Get Report), down 1 cent to $27.20; Genta ( GNTA), up 9 cents to $2.14; Guidant ( GDT), up $3.60 to $72.35; Merck ( MRK), down 23 cents to $27.89; and Johnson & Johnson ( JNJ - Get Report), down $1.42 to $60.41.