The tradition of labor solidarity left the AFL-CIO's national headquarters virtually shut down yesterday when 12 of the federation's lowest paid employes struck for higher pay and more than 400 other AFL-CIO workers honored their picket line by staying off the job.

The strike by a 12-member unit of researchers, health specialists, analysts and clerical workers who earn an average of $16,000 a year left the labor federation's seven-story building largely deserted, because the separate unions representing the bulk of the work force voted to support the strike.

"We are asking for parity" with some other AFL-CIO units, "a very modest demand," said Sandra Polaski, a spokeswoman for Local 35 of The Newspaper Guild, which represents the strikers.

The walkout is the first strike at the AFL-CIO headquarters in 15 years.

The strikers are employed by the AFL-CIO Food and Allied Service Trades department, which conducts research for 15 unions in the food, hotel and other service industries. The AFL-CIO, a federation of 96 unions, has nine such departments, some of which bargain separate contracts with their staff employes.

"This strike is not against the AFL-CIO, and it does not affect us directly. FAST is a separate employer, and this is not our strike," said AFL-CIO spokesman Rex Hardesty, one of several dozen management employes who reported to work. Outside AFL-CIO headquarters at 815 16th St. NW, dozens of workers stood on picket lines or gathered on the sidewalk, deciding whether to return home or await a possible quick settlement. Most went home.

Polaski said strikers would not discuss specifics of the dispute, but union sources said the key issue is that FAST professional staffers, roughly half holding graduate degrees, receive starting pay of $14,000, and are paid roughly $10,000 less than other AFL-CIO staffers with comparable duties and experience.

FAST President Robert Harbrant, who negotiated for the department, was not available for comment.

The AFL-CIO in recent months concluded contract negotiations with the Office and Professional Employees International union and with another unit of the Guild. But the FAST contract expired Wednesday without a settlement, prompting the strike. The OPEIU, which represents clerical workers, has a contract with a pay scale ranging from $18,000 to $25,000, while the Guild, which represents professionals, has pay scales ranging from $23,300 to $63,000, with the higher pay going to veteran AFL-CIO lobbyists, economists and other experts.

FAST employes lobbied for support of other AFL-CIO employes in a series of recent leaflets that pictured various employes, listing their salary and education. "We got tremendous support, and a lot of people started wearing 'I support FAST' buttons," one striker said. OPEIU and the other Guild members voted Tuesday to support the strike.

"We wished they had set up their picket line at one end of the building" instead of the main entrance," Hardesty said. "But they didn't." The AFL-CIO put up a sign marking its side entrance on I Street for "non-FAST" employes, but few workers attempted to cross the picket line. AFL-CIO President Lane Kirkland was on vacation, but Secretary-Treasurer Thomas Donahue reported to work with management staff, who manned telephones.

Hardesty said those who honored the strike presumably would not be paid.

Their failure to report to work apparently violates their contract, he said, but added that no action would be taken against them, other than losing pay.