The apparent unbound bilirubin concentration by the “peroxidase” method (U) and the total unconjugated bilirubin in blood (T), albumin-bound bilirubin (B), and reserve bilirubin binding capacity (A) by the bilirubin hematofluorometer were measured in 164 specimens from 98 neonates and in a series of artifactual specimens, made by adding bilirubin to the blood of a single adult donor. Linear correlations between U and (B/R) were found for both the prepared specimens (r = 0.99) and the clinical specimens (r = 0.87), with the slopes of the regression lines being close to the reciprocal of the albumin-bilirubin binding constant, a prediction of the mass action law. An excellent linear correlation was observed for the prepared specimens (r = 0.96) between U and (1B), the concentration of bilirubin bound to low-affinity secondary sites (“loosely bound bilirubin”). A simple model for low-affinity binding of bilirubin in blood predicts this simple relation. A significant linear correlation between U and (T B) was found for the clinical specimens, although the correlation was less good (r = 0.72), as one would expect. The demonstrated simple linear relationships between U, (B/A), and (T B) support the hypothesis that both the hematofluorometer and peroxidase methods provide valid measurements of bilirubin binding status.

We describe the rapid, inexpensive fluorometry of hemoglobin in undiluted whole blood. The procedure consists only of adding a standard quantity of a fluorescent dye to a measured volume (‘-‘15 .tL) of blood, together with some solubilizing detergent. The assay is based on the attenuation of the dye’s fluorescence (excited within the region 400-440 nm) that results from the competitive absorption of exciting light by the hemoglobin present-the “inner filter effect.” The wavelength that one can use is optional and will determine which dyes can be used. Measurements are made with the hematofluorometer, a “frontface” filter fluorometer (Blumberg et al., J. Lab. C/in. Med. 89: 7 12-723, 1977). We demonstrate the validity of the method for two dyes, rhodamine B and fluorescein dibutyrate, which we used with hematofluorometers that were designed to determine blood zinc protoporphyrin and bilirubin, respectively. Our method exhibited a standard error of about 4 g of hemoglobin per liter vs the comparison method (Coulter Counter method, for which the CV is 1.2%). The CV is about 3%. The method seems appropriate for “field” use (i.e., use outside the laboratory) in anemia-screening programs.

Central nervous system dysfunction in workers occupationally exposed to lead was investigated by means of performance tests. The test scores of lead-exposed workers were compared with those of control groups (steel workers, papermill workers and farmers). It was found that secondary lead smelter workers showed significantly poorer performance scores than the nonexposed, control groups. The group differences between steel workers and lead workers in test scores were not attributable to differences in age or education. In the lead-exposed workers correlations between test scores and indicators of lead absorption (particularly blood lead and zinc protophyrin levels) were analyzed. Increases in zinc protoporphyrin levels were found to be highly correlated with decreases in test scores. Lower performance test scores were consistent with a sizeable prevalence of central nervous system symptoms among secondary lead smelter workers. Moreover, lead workers without central nervous system symptoms also showed decrements in performance test scores which were also correlated with elevated zinc protoporphyrin levels. The data indicate that certain behavioral tests might be important tools for studying subclinical central nervous system dysfunction due to lead toxicity; significant correlations between zinc protoporphyrin levels and behavioral test scores are considered to be consistent with an etiologic relationship between decrement in performance scores and lead effects on the central nervous system.

A subgroup of workers from a secondary lead smelter was defined to include those with blood lead levels not exceeding 80 microgram/100 ml and with no past history of elevated blood lead. Central nervous system symptoms (tiredness, sleeplessness, irritability, headache) were reported by 55% of the group and muscle and joint pain by 39%. Zinc protoporphyrin (ZPP) levels were elevated in 71% of cases. Low hemoglobin levels (less than 14 gm/100 ml) were found in more than a third of the workers. While BUN and creatinine were mostly in the normal range, there was nevertheless a correlation between ZPP and both BUN and creatinine. Reduced nerve-conduction velocities were present in 25% of the group; this was not significantly different from findings in a control group. The data indicate that a blood level of 80 microgram/100 ml is an inappropriate biological guide in the prevention of lead disease.