Table 1

Number of blood samples selected for organochlorine compound assays by case-control status and by reason for selection, Long Island Breast Cancer Study Project, 1996–1997

Subject statusCases (n)Controls (n)Total (n)
InvasiveIn situAll
(A) Respondent to main questionnaire150815563064
(B)  Blood donor110211412243
(C)   Blood samples selected for organochlorine compound assays (= E + F)6011847854291214
(D)    Reason for selection:
(E)     Random samplea415415406821
(F)     Specifically selected (= G + H + I + J + K)18618437023393
(G)      In situ cases selected128128
(H)      African Americans not randomly selected52328
(I)      Selected as in situ, but invasive4242
(J)      Selected as invasive, but in situ5656
(K)      Donated second sample139139
(L)   Blood samples included in most statistical analyses (= C − K)b4621846464291075
  • a All of the samples donated by in situ cases with sufficient amounts of blood/DNA were selected for analyses (see “Materials and Methods”).

  • b Excludes second samples (see “Materials and Methods”).