Nichols Institute Reports 44% Jump in Earnings for 1990 : Fiscal health: The gain was despite an 8% decline in fourth-quarter profits that caused its stock price to plunge.

Nichols Institute, a growing chain of medical laboratories based here, said Friday that its earnings jumped 44% last year to $6.8 million, up from $4.7 million in 1989.

The earnings gain for the year came despite an 8% decline in fourth-quarter profits, which fell to $1.26 million from $1.37 million a year earlier. The company had previously said that it expected a decline in earnings for the latest three months.

Revenue for 1990 was $174.8 million, up 35% from $129.7 million the previous year.

For the fourth quarter, revenue rose to $45.5 million, up 33% from $34.2 million during the corresponding three months of 1989.

Nichols had told Wall Street analysts in early January that fourth-quarter earnings would be poorer than originally expected for several reasons, including problems associated with the acquisition of a laboratory in Portland, Ore., and delays in completing the purchase of outpatient laboratories in Texas.

In the three trading days after Nichols’ Jan. 3 announcement, the company’s per-share stock price plunged 37.8%, from $16.50 to $10.25. The stock closed Friday at $13.25 a share, up 37.5 cents on the American Stock Exchange.

Dr. Albert L. Nichols, the company’s chairman and chief executive, said in a prepared statement Friday that overall 1990 results reflect “continued steady growth in revenues and earnings” for the company’s reference laboratory in San Juan Capistrano, its Midwest regional laboratories and its diagnostic kit business.

Ken Bohringer, a securities analyst with Prudential-Bache Research in New York, said he believes the earnings slump in late 1990 represented problems that Nichols is overcoming. “I think they will have it corrected by the end of this quarter,” he said.