No specific laboratory tests are available for making a diagnosis of AFE, yet several tests
have been proposed to increase the index of suspicion for this diagnosis (Table 2). In 1976,
Resnik et al,111 first reported the identification of amniotic fluid debris in central venous
blood aspirated from the distal lumen of a pulmonary arterial catheter of a survivor woman
with AFE. This finding has been reported several times.112–115 However, in the Clark et al’s
national registry19 only 4 of 8 women (50%) had this finding. In addition, the detection of
squamous cells in the pulmonary arterial circulation is not pathognomonic for AFE since
they have been identified in 21–100% of pregnant women without AFE116–119 and in non
pregnant women.118,120 Unfortunately, reliable differentiation between maternal and fetal
squamous cells is still difficult in the clinical setting. Thus, the detection of squamous cells
in the maternal pulmonary arterial circulation is not sufficient for the diagnosis of AFE. The
identification of such findings in the maternal pulmonary arterial circulation is supportive of
the diagnosis when they are found in large numbers, are coated with neutrophils, and/or they
are accompanied by other fetal debris.