Radioimmunoassay for plasma histamine: a study of false positive and false negative values

In order to achieve a correct diagnosis of drug anaphylaxisusing a radioimmunoassay devoid of interferences, we have studiedfactors leading to false positive or false negative values ofplasma histamine. Different steps in sample collection werestudied systematically in 30 normal volunteers. False positivevalues were found in haemolysed samples, with histamine concentrationsbeing correlated with haemoglobin concentrations, and whereplasma was aspirated from the white-cell layer. There was nosignificant increase when a tourniquet or vacuum tubes wereused, or when blood tubes were left at 4 °C overnight. In12 patients who experienced an anaphylactic reaction, histaminedisappeared from blood 10 times more slowly than expected. Falsenegative values were found in two pregnant women and one heparinizedpatient. Histamine was remarkably stable in vitro in blood orplasma samples, whereas it disappeared rapidly when plasma froma pregnant woman or a heparinized patient was added to the sample.We conclude that false positive and false negative values arerare when using this radioimmunoassay.     

Congenital lung malformation: Evaluation of prenatal and postnatal radiological findings

Background and objective:   This study evaluated the accuracy of prenatal MRI and postnatal CT imaging in the identification of congenital cystic adenomatoid malformation and bronchopulmonary sequestration by comparison with histological analysis.
Methods:   Over a 3-year period, 15 patients with lung malformations diagnosed prenatally by ultrasound were referred for prenatal MRI, and all were investigated postnatally by chest CT. All asymptomatic newborns with unresolved lesions underwent elective surgery by thoracoscopy. All surgical specimens were analysed histologically.
Results:   Among the 15 patients with an abnormality diagnosed by ultrasound, prenatal MRI findings differed from the final histological diagnosis with respect to extent ( n  = 3), type of lesion ( n  = 1) and aberrant vessel identification ( n  = 4). Postnatal chest CT failed to visualize the aberrant vessel in one patient. Complete regression of the lesion was noted in two patients with bronchopulmonary sequestration, and in one patient with congenital cystic adenomatoid malformation and was confirmed by CT. Elective thoracoscopic lobectomy of the affected lobe was performed for 12 patients. Two conversions to thoracotomy were required. All operated patients had an uneventful hospital course.
Conclusions:   Prenatal MRI is less accurate than postnatal CT scan, which remains the most reliable diagnostic modality to specify the location and extent and kind of lesions.