1295 COLOUR-BLIND LABORATORY TECHNOLOGISTS tests for colour blindness on of our laboratory staff and found 6 out of 94 with colour defects. We further tested them to assess the implications of such defects in a clinical laboratory. The colour blindness test used was that of Ishihara.I All 6 had red/green, and 4 out of the 6 also had yellow/blue identification problems. All 6 subjects were unable to see acidfast bacilli on a sputum smear as displayed by the ZiehlNeelsen staining technique with malachite green as counterstain. No problems were encountered with gram stains, however. Only 1 out of the 6 subjects had the opportunity of examining a fluorescent stain for tubercle bacilli. He reported that he could not see the "green fluorescence" and that the bacilli were "dirty-white" and the so-called red background was yellow in patches. We also investigated how these defects would affect their ability to use diagnostic strips for urine and blood chemical analysis. All subjects were asked if they could differentiate between negative and positive reactions on ’N-Multistix’ (Ames Co, Elkhart, Indiana). 2 subjects identified the colour of the glucose strip inaccurately but were nevertheless able to see a colour change from negative to positive. We suggest that all laboratory workers be screened for colour-blindness defects and that those who fail be placed in positions where they are not called upon to use colour differentiation in routine analysis. Acid/alkali titrations involving a colour change or where titrations are continued to a specific colour end-point, are obvious examples.

SIR,-We recently conducted

some

Natal Blood Transfusion 2356 Durban 4000, South Africa

Service,

cation for phototherapy was a serum unconjugated bilirubin level ≥10 mg/dl in the first 48 h after birth. The hyperbilirubineemia was ascribed in all cases to a developmental (physiological) jaundice. The presence of the bilirubin-albumin photoadduct was determined by precipitation of serum proteins through the addition of acetone in a fivefold excess over water (v/v). In sera from babies taken before irradiation, most of the bilirubin was extracted by acetone; removal was complete only after redissolution of the precipitated material in the presence of 7 mol/1 guanidine and reprecipitation with acetone. On the other hand, in sera from the same babies taken after they had been irradiated for at least 7-9 h bilirubin remained bound even after addition of denaturant. The presence of bilirubin in the samples was monitored by fluorescence emission (X=460 nm) and fluorescence excitation 530 nm) spectroscopy (figure). Ammonium sulphate precipitation of serum proteins showed that the photoadduct specifically appeared in the albumin fraction. In general, the amount of observed photoadduct was found to depend on the amount of light energy received during phototherapy. The photoadduct disappeared between 15 and 20 days after treatment. This period of time is coincident with the normal turnover of the serum albumin. This is the first demonstration of minor damage during phototherapy for jaundice. However, the exact yield of the photoadduct in sera of treated infants and its real importance have not yet been clarified. The amount of photoadduct is probably low because the adduct detectable by fluorescence spec-

B. J. VORSTER L. V. MILNER

MODIFICATION OF SERUM ALBUMIN DURING PHOTOTHERAPY OF JAUNDICED NEWBORN BABIES

SIR,-Phototherapy for jaundice in newborn babies has been in extensive use for years2 and appreciable photodamage has been generally assumed not to occur. However, we have shown that in-vitro visible-light irradiation of the 1:1 bilirubin-human serum albumin complex modifies specific aminoacid residues so that the protein is partly denatured and the bilirubin or its photoproduct(s) cannot be removed from albumin, even after acetone-induced precipitation of the complex in the presence of 7 mol/1 guanidine. 3,4 The formation of a bilirubin-albumin covalent photoadduct was confirmed by the isolation of one peptide containing bilirubin after fragmentaion of protein which had been irradiated for 30 min and subsequent fractionation of the peptides by column chroma-

tography.4 To investigate whether binding takes place also during phototherapy we analysed the sera of 29 hyperbilirubinxmic full-term newborn babies before and after continuous light treatment with a set of a F20T12/BB Westinghouse lamps (the intensity of the irradiation at the level of the infants was 22 p.W/cm2/nm in the wavelength range 440-470 nm). The indi-

1. Ishihara S. Tests for

colour-blindness, 15th ed. Tokyo: Kanehara Shuppan

Co., 1960.

2. McDonagh AF. The photochemistry and photometabolism of bilirubin. In: Odell GB, Schaffer R, Simonoppulos AP, eds. Phototherapy m the newborn: an overview. Washington, D.C., National Academy of Sciences, 1974: 56-73. 3. Rubaltelli FF, Jori G. Visible light irradiation of human and bovine serum albumin-bilirubin complex. Photochem Photobiol 1979; 29: 991-1000. 4. Jori G, Rossi E, Rubaltelli FF. Evidence for visible light-induced covalent binding between bilirubin and serum albumin "in vitro" and "in vivo". 7th annual meeting of the American Society for Photobiology 1979; abst

p 176.

fluorescence emission (above) and excitation (below) spectra of bilirubin in sera of jaundiced newborn babies (-----)and in acetone-extracted solution (-.-.-.-).

Typical

In sera of unirradiated infants the typical fluorescence excitation and emission spectra of bilirubin are absent from an aqueous solution of serum proteins after acetone extraction, redissolution in 7 mol/1 guanidine, and acetone reprecipitation. After phototherapy, the sera of the same infants retained a detectable amount of bilirubin bound to serum proteins even after acetone-induced precipitation in the presence of 7 mol/l guanidine (