Three medical groups have collaborated in an effort to inform their members that there is only about one month left to submit claims for money they may be owed as part of the multi-million-dollar settlement in a class-action lawsuit against the Cigna Corp.

The American Medical Association, the American Medical Group Association and the Medical Group Management Association sent letters to more than 147,000 member physicians and medical group practice administrators to raise awareness about the available compensation in the $540 million settlement of a five-year-old lawsuit.

Cigna will pay physicians about $70 million in the settlement over charges that the giant managed-care organization conspired to systematically underpay physicians for their services. The deadline for filing claims is Feb. 18.