A relatively mild hurricane season and better investment results boosted Quest Diagnostics Inc.‘s third-quarter sales and earnings.

The Madison, N.J.-based molecular diagnostics maker said net revenues for the three months ended Sept. 30 rose 3.9 percent to $1.9 billion, compared with $1.83 billion during the same period last year.

Quarterly net income surged to $192.2 million, up 73.5 percent compared with $110.8 million during the third quarter of 2008.

Quest cited a $0.03-per-share-charge from the write-down of an equity investment during the year ago quarter, and a $0.02-per-share impact from hurricanes, as part of the reason for the improvement.

Chairman and CEO Surya Mohapatra said the results also reflected increased demand for Quest’s cancer, sexually transmitted disease, allergy and Vitamin D tests.

The results prompted the company to raise its guidance for the full. Quest said it expects earnings per diluted share from continuing operations to be $3.80-$3.85, compared with a previous forecast of $3.70-$3.80 on revenue growth of about 3 percent.

Some of that growth, should it come to pass, will likely depend on the severity of the flu season. Quest subsidiary Focus Diagnostics recently won another emergency authorization from the Food & Drug Administration for its “real-time” molecular test for the Swine Flu.

The test uses polymerase chain reaction technology to identify RNA from the H1N1 influenza virus, enabling it to distinguish swine flu from other, seasonal variants.