MEASUREMENT OF FECAL LACTOFERRIN AS A MARKER OF FECAL LEUKOCYTES

While diarrheal illnesses are extremely common in communities and hospitals throughout the world, an etiologic diagnosis may be expensive and cost-ineffective. Although the presence of fecal leukocytes are helpful in the diagnosis and specific therapy of inflammatory diarrheas, this requires prompt microscopic examination of fecal specimens (preferably obtained in a cup rather than a swab or diaper) by a trained observer. We developed a simple, sensitive test for the detection of leukocytes in fecal specimens using antilactoferrin antibody. Whereas radial immunodiffusion detected 0.02-mu-g of lactoferrin (LF) per mu-l or greater-than-or-equal-to 2,000 leukocytes per mu-l, latex agglutination (LA) readily detected greater-than-or-equal-to 0.001-mu-g of LF per mu-l or greater-than-or-equal-to 200 leukocytes per mu-l added to stool specimens. Despite the destruction or loss of morphologic leukocytes on storage for 1 to 7 days at 4-degrees-C or placement of specimens on swabs, measurable LF remained stable. Initial studies of stool specimens from six patients with Salmonella or Clostridium difficile enteritis were positive and those from three controls were negative for LF by LA. Of 17 children in Brazil with inflammatory diarrhea (greater-than-or-equal-to 1 leukocyte per high-power field), 16 (94%) had LF titers of > 1:50 by LA, whereas only 3 of 12 fecal specimens with < 1 leukocyte per high-power field on methylene blue examination and none of 7 normal control specimens had an LF titer of > 1:50 by LA. Of 16 fecal specimens from patients with C. difficile diarrhea (cytotoxin titers, greater-than-or-equal-to 1:1,000), 95% (n = 15) had detectable LF by LA (in titers of 1:100 to 1:800). Finally, of 48 fecal specimens from healthy adult U.S. volunteers before and after experimental shigellosis and of 29 fecal specimens from children with documented shigellosis and hospitalized controls in northeastern Brazil, fecal LF titers ranged from 1:200 to greater-than-or-equal-to 1:5,000 in 96% (25 of 26) samples from patients with shigellosis (and reported positive for fecal leukocytes), while 51 controls consistently had fecal LF titers of less-than-or-equal-to 1:200. We conclude that fecal LF is a useful marker for fecal leukocytes, even when they are morphologically lost on swab specimens or when they are destroyed on transport or storage or by cytotoxic fecal specimens.