TABLE 2.

Additional laboratory studies, pertussis outbreaks, New York, September 15, 1998 to November 14, 1999

Laboratory study	nc	Results of PCR for B. pertussis DNA
		Private laboratory	NYSDOH/WC
PCRa	33	20 PCR positive	8 PCR positive
		13 PCR negative	25 PCR negative
QA testb	10	4 PCR positive for B. pertussis DNA	4 PCR positive for B. pertussis DNA
		2 nonpertussis specimens PCR positive	6 nonpertussis specimens PCR negative
		4 nonpertussis PCR negative

^aPCR for B. pertussis DNA was performed by the private laboratory and NYSDOH/WC pertussis laboratory on dual samples from the same patients.

^bSpecimens were prepared by NYSHD/WC Proficiency Testing Laboratory (four with B. pertussis) and blind PCR tested by the private laboratory and NYSDH/WC pertussis laboratory.

^cn, no. of samples studied.