Existing-home sales nationally slipped 0.8 percent in April from March, even as the market in many areas remained glutted with heavily discounted foreclosures and fixed interest rates fell.

"Another disappointing housing report," said IHS Global Insight housing economist Patrick Newport.

Sales were 12.9 percent below April 2010, when the federal tax credit expired, the National Association of Realtors reported Thursday.

Houses purchased with the tax credit continued to close in May, boosting the sales numbers. Then sales fell off dramatically for several months.

The news for April was better in the eight-county Philadelphia area tracked by the Prudential Fox & Roach HomExpert Report, with sales 6.6 percent above March.

But year-over-year sales data were worse than in the rest of the country, with a drop of 27.1 percent from April 2010, HomExpert reported. The absence of the tax credit played a role, experts agreed.

Some real estate experts, however, said the lower foreclosure inventory in this area compared with regions where distressed sales account for 40 percent of the market may be the reason for the larger decline here.

The median price, $195,000, was down 2.5 percent from $200,000 in April 2010.

Nationally, the median was $163,700, down 5.5 percent from $173,200 a year earlier.

Association chief economist Lawrence Yun said, "Unnecessarily tight credit is continuing to restrain the market, along with a steady level of low appraisals that result in contract cancellations."

In a national survey of Realtors by the association, 11 percent reported a sales contract canceled in April because an appraisal had come in below the negotiated price.

Ten percent reported a contract delayed, and 14 percent said a contract had been renegotiated to a lower price as a result of a low appraisal.

Although he's had no problems yet this year, "last year I had two low appraisals, one of which resulted in a termination," said John Badalamenti, associate broker at Prudential Fox & Roach in Wayne.

"When an appraiser asks for directions to a listing and he/she asks, 'What's a Blue Route?' - it's kind of a red flag," he said. "Perhaps an appraiser familiar with the area would be more suited."

Although agent Ruth Feldman of Weichert Realtors McCarthy Associates in Mount Airy has heard "horror stories" from others, she has yet to experience one, she said.

"I represented a buyer recently where the appraisal came in a bit low, and the seller came down in price by the same amount," she said.

Feldman meets and talks with the appraiser "to get a feel for how local he or she is and how much they know about the area."

Under new appraisal rules, the mortgage broker is not allowed to contact the appraiser, but the real estate agent can do so.

Although fixed interest rates continue to fall - 4.61 percent for 30-year loans Thursday - Yun said sales were being held back 15 to 20 percent "due to the very restrictive loan underwriting standards."

And credit is not likely to loosen soon, Newport said.

"With house prices falling, lenders are likely to demand higher down payments, given that the collateral will lose value in the near term," he said.

Freddie Mac and Fannie Mae will lower the maximum conforming loan limit from $729,750 to $625,500 on Oct. 1. That means buyers in areas where houses cost more will have to pay interest rates higher than those buying houses for less than $625,000.

If all of this and an unabating foreclosure crisis are already weighing heavily on home sales, add higher gasoline prices to the mix.

Coldwell Banker's national survey of its agents found that buyers were choosing houses closer to work, were back to looking for space for a home office, and were even considering urban living.

"Rising fuel costs and a person's decision to commute or perhaps work remotely are additional factors of the decision home buyers must consider," said Coldwell Banker chief executive Jim Gillespie.

Contact real estate writer Alan J. Heavens at 215-854-2472, aheavens@phillynews.com, or @alheavens on Twitter.