Moody's Investors Service placed the long-term debt ratings of MBNA Corp. under review for a possible downgrading. About $3.5 billion worth of securities were affected.

Moody's cited the same worries it had Nov. 6, when it first gave the company a negative outlook.

The rating agency said it is "concerned that the allegiance of cardholders in nonendorsed or nonexclusive affinity programs may be weaker and more price sensitive than with the stronger endorsed affinity programs that have historically made up a larger portion of MBNA's portfolio."

MBNA currently enjoys the highest debt rating among credit card specialty banks.

Several bond analysts were puzzled, saying they didn't understand what had changed since November.

"This wasn't a result of what came out of the fourth-quarter numbers," said Mark Geralimo, a bank bond analyst at Bear, Stearns & Co.

"I don't understand how their view changed so quickly from two months ago in the face of fair fourth-quarter numbers, which they themselves have acknowledged in their announcement," said Jean I. Sievert, a bank bond analyst at Chase Securities.

"They seem concerned about the allegiance of cardholders, but so far the numbers haven't borne out any negatives in that regard," Mr. Geralimo said.

Others, however, agreed with the Moody's assessment.

"The action reflects a deterioration in the type of customers MBNA is marketing and its more recent growth patterns," said Katie Rossow, a bank bond analyst at Furman Selz. "That's fair."

Indeed, Ms. Rossow pointed to systemic risk for credit card companies.

"There's a rapid buildup in consumer indebtedness at the same time that there's a drop-off in the economy," said Ms. Rossow. "That's a one-way ticket. The ones who get hit first are the ones that are on the top of the rating spectrum."

Subscribe Now

Access to authoritative analysis and perspective and our data-driven report series.

14-Day Free Trial

No credit card required. Complete access to articles, breaking news and industry data.