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EFFECTS OF INACTIVATING HTLV-III ON LABORATORY TESTS
99
EFFECTS OF INACTIVATING HTLV-III ON LABORATORY TESTS the effects of heat treatment of laboratory tests include Dr Evans and Dr serum/plasma Shanson’s contribution (June 22, p 1458) on aminoglycoside assays. We report here on the stability of other antimicrobial agents to heating intended to destroy HTLV-III. Sera were "spiked" to concentrations likely to be the greatest encountered clinically and held at 56 °C. To pooled normal human serum was added gentamicin, tobramycin, netilmicin, amikacin, and penicillin (20 mg/1); vancomycin, cefuroxime, and flucytosine (40 mg/1); rifampicin and chloramphenicol (25 mg/l)-, and amoxycillin (10 mg/1). Sera were held at 56°C and samples were removed at zero, 1, 2, and 3 h and stored at -70°C before assay by large plate agar diffusion technique. The chloramphenicol samples were also assayed by HPLC and the aminoglycosides and vancomycin were also assayed by polarising spectrofluorimetry (Abbott
SIR,-Lancet letters
on
on
Laboratories). All sera spiked with aminoglycosides showed no change in concentration when measured by spectrofluorimetry. When assayed microbiologically, with Klebsiella edwardsii NCTC 10896 as the indicator organism, netilmicin and tobramycin showed no change at 2 h and a slight reduction (not more than 10%) at 3 h, while gentamicin exhibited no change at 1 h, a 5% reduction at 2 h and not
more
than 10%
at
3 h. Other antibiotics %
Antibiotic Penicilhn
1 h 74
Cefuroxime
57 100 65 98 87
Amoxycillin Rifampicin Chloramphemcol Flucytosine
were
less stable:
remaining at: 2h 60 48 75 48
90 84
3h 50 37 73 40 89 75
We conclude that sera for the assay of some antibiotics can be treated at 56°C for 30 min without impairing the accuracy of the determination. H. A. HOLT
Department of Medical MJcroblOlogy,
.. BYWATER
Southmead Hospital, BnstolBSlO5NB
SIR,-The letter (May 18,
’
p
1160)
on
D. S. REEVES
(3-propiolactone (BPL)
of blood and plasma sent for chemical analysis has prompted several inquiries about effects on haematological measurements. We have studied this aspect too. Venous blood was collected from twenty subjects (some with abnormal blood counts). Specimens were divided and BPL (Sigma) was added to whole blood and to citrated plasma to a final concentration of 0-25% and treated and untreated EDTA specimens were kept at 25°C for 3 h before analysis on a Coulter S-plus counter 3, 6, 24, and 48 h after treatment (see table). Blood films made at various times after BPL treatment showed neutrophil disintegration, starting within 2 h, although a differential count was possible for up to 6 h. After 48 h the platelet count was significantly lower, but in practice this would only be relevant if routine specimens were treated at weekends. Coagulation studies revealed a marked increase in kaolin cephalin clotting time (KCCT), Quick’s prothrombin time, and thrombin time. Two-stage factor VIII assays were also affected (Dr D. Austin, personal communication). Erythrocyte sedimentation rate was reduced.
Plasma folate, measured by a microbiological assay, was also lower. Colorimetric assays of plasma iron were not affected. Our study suggests that BPL does not interfere with the estimation of haemoglobin or total white cell or platelet counts. The small increase in MCV is unlikely to be clinically significant. The lymphocyte count is unreliable on the Coulter S-plus analyser, but is unaffected on the Technicon H 6000. Differential white cell counts can be done by eye if the blood film is prepared promptly. Coagulation studies are significantly affected and BPL should not be added to specimens taken for such purposes. Treatment should be done with care since BPL is an alkylating agent, although the products formed after incubation with blood are not.
We thank Mrs A. Patterson for her
Departments of Chemical
help.
Pathology
and
Haematology, John Radcliffe Hospital,
M.J. BALL
Oxford OX3 9DU
F. G. BOLTON
1. IARC
IV.
monographs on the evaluation of the carcinogenic risk of chemicals to man: vol Lyon: IARC, 1973: 259-69.
SIR,-We have studied the effect of heat inactivation on biochemical indices by heating serum at 560C for 1 h, representinga "worst case" situation, to see whether time had any critical effect. The nine sera we examined were from patients with various biochemical abnormalities in their blood, thus simulating the situation that might occur with patients infected with HTLV-III. There was no practical difference between heated and unheated serum in respect of results for sodium, potassium, chloride, calcium, urate, glucose, total protein, and creatinine. If the results for one serum specimen were excluded, phosphorus, urea, and bilirubin also gave satisfactory results. Unlike other reports to date, our results were obtained using manual techniques, which is important if smaller laboratories are faced with the problem of examining sera from HTLV-III-infected patients and feel that heat treatment is an essential part of their safety procedures. Department of Laboratory Medicine, Ruchill Hospital, Glasgow G20 9NB
A. GOW R. J. FALLON
treatment
EFFECT OF &bgr;-PROPIOLACTONE ON AUTOMATED CELL COUNTS AND COAGULATION STUDIES
*p
tp
(n = 20)
(n = 40)
THE MARSUPIAL MOTHER
SIR,-The article by Dr Whitelaw and Katharine Sleath (May 25,
1206) does much to put the apparently "miraculous" results of the Bogota home-care programme for low birthweight (LBW) babies into perspective. More importantly, it highlights an innovative attempt to rationalise care of the LBW baby in the developing world. Many medical practices in the Third World have been imported from the developed world with little thought to their suitability. A growing awareness of the inadequacies of the Western medical model to deal with health problems in the developing world underlies the current World Health Organisation emphasis on community based primary health care. About 19 million LBW babies are born in the developing world every year.Most of these will be born in rural areas, and even if the baby is born in hospital the maternity unit is likely to be overcrowded and have only basic facilities for care of the LBW baby. If the baby survives, the unexpectedly prolonged hospital stay will disrupt and cause financial hardship in a subsistence level family already struggling for survival. He may be discharged to a hostile environment and to a family which is much less stable than the one p
in which he was conceived. Such is the situation in Maua Hospital, in rural Kenya, where about 9% of the 4000 babies born each year weigh less than 2500 g. Care of these babies is basic but follows the traditional western model. The babies are nursed in a special nursery, kept warm, fed early with expressed breast milk, and treated with antibiotics if infection is suspected. They are nursed by inexperienced staff, assisted as much as possible by the mothers. There are no incubators or ventilators. In the six months of our study 45 (33-1%) of the LBW babies born died in hospital-16 (89%) of the babies under 1500 g, 15 (58%) of the babies weighing 1500-1999 g, and 14 (15%)
EFFECTS OF INACTIVATING HTLV-III ON LABORATORY TESTS the effects of heat treatment of laboratory tests include Dr Evans and Dr serum/plasma Shanson’s contribution (June 22, p 1458) on aminoglycoside assays. We report here on the stability of other antimicrobial agents to heating intended to destroy HTLV-III. Sera were "spiked" to concentrations likely to be the greatest encountered clinically and held at 56 °C. To pooled normal human serum was added gentamicin, tobramycin, netilmicin, amikacin, and penicillin (20 mg/1); vancomycin, cefuroxime, and flucytosine (40 mg/1); rifampicin and chloramphenicol (25 mg/l)-, and amoxycillin (10 mg/1). Sera were held at 56°C and samples were removed at zero, 1, 2, and 3 h and stored at -70°C before assay by large plate agar diffusion technique. The chloramphenicol samples were also assayed by HPLC and the aminoglycosides and vancomycin were also assayed by polarising spectrofluorimetry (Abbott
SIR,-Lancet letters
on
on
Laboratories). All sera spiked with aminoglycosides showed no change in concentration when measured by spectrofluorimetry. When assayed microbiologically, with Klebsiella edwardsii NCTC 10896 as the indicator organism, netilmicin and tobramycin showed no change at 2 h and a slight reduction (not more than 10%) at 3 h, while gentamicin exhibited no change at 1 h, a 5% reduction at 2 h and not
more
than 10%
at
3 h. Other antibiotics %
Antibiotic Penicilhn
1 h 74
Cefuroxime
57 100 65 98 87
Amoxycillin Rifampicin Chloramphemcol Flucytosine
were
less stable:
remaining at: 2h 60 48 75 48
90 84
3h 50 37 73 40 89 75
We conclude that sera for the assay of some antibiotics can be treated at 56°C for 30 min without impairing the accuracy of the determination. H. A. HOLT
Department of Medical MJcroblOlogy,
.. BYWATER
Southmead Hospital, BnstolBSlO5NB
SIR,-The letter (May 18,
’
p
1160)
on
D. S. REEVES
(3-propiolactone (BPL)
of blood and plasma sent for chemical analysis has prompted several inquiries about effects on haematological measurements. We have studied this aspect too. Venous blood was collected from twenty subjects (some with abnormal blood counts). Specimens were divided and BPL (Sigma) was added to whole blood and to citrated plasma to a final concentration of 0-25% and treated and untreated EDTA specimens were kept at 25°C for 3 h before analysis on a Coulter S-plus counter 3, 6, 24, and 48 h after treatment (see table). Blood films made at various times after BPL treatment showed neutrophil disintegration, starting within 2 h, although a differential count was possible for up to 6 h. After 48 h the platelet count was significantly lower, but in practice this would only be relevant if routine specimens were treated at weekends. Coagulation studies revealed a marked increase in kaolin cephalin clotting time (KCCT), Quick’s prothrombin time, and thrombin time. Two-stage factor VIII assays were also affected (Dr D. Austin, personal communication). Erythrocyte sedimentation rate was reduced.
Plasma folate, measured by a microbiological assay, was also lower. Colorimetric assays of plasma iron were not affected. Our study suggests that BPL does not interfere with the estimation of haemoglobin or total white cell or platelet counts. The small increase in MCV is unlikely to be clinically significant. The lymphocyte count is unreliable on the Coulter S-plus analyser, but is unaffected on the Technicon H 6000. Differential white cell counts can be done by eye if the blood film is prepared promptly. Coagulation studies are significantly affected and BPL should not be added to specimens taken for such purposes. Treatment should be done with care since BPL is an alkylating agent, although the products formed after incubation with blood are not.
We thank Mrs A. Patterson for her
Departments of Chemical
help.
Pathology
and
Haematology, John Radcliffe Hospital,
M.J. BALL
Oxford OX3 9DU
F. G. BOLTON
1. IARC
IV.
monographs on the evaluation of the carcinogenic risk of chemicals to man: vol Lyon: IARC, 1973: 259-69.
SIR,-We have studied the effect of heat inactivation on biochemical indices by heating serum at 560C for 1 h, representinga "worst case" situation, to see whether time had any critical effect. The nine sera we examined were from patients with various biochemical abnormalities in their blood, thus simulating the situation that might occur with patients infected with HTLV-III. There was no practical difference between heated and unheated serum in respect of results for sodium, potassium, chloride, calcium, urate, glucose, total protein, and creatinine. If the results for one serum specimen were excluded, phosphorus, urea, and bilirubin also gave satisfactory results. Unlike other reports to date, our results were obtained using manual techniques, which is important if smaller laboratories are faced with the problem of examining sera from HTLV-III-infected patients and feel that heat treatment is an essential part of their safety procedures. Department of Laboratory Medicine, Ruchill Hospital, Glasgow G20 9NB
A. GOW R. J. FALLON
treatment
EFFECT OF &bgr;-PROPIOLACTONE ON AUTOMATED CELL COUNTS AND COAGULATION STUDIES
*p
tp
(n = 20)
(n = 40)
THE MARSUPIAL MOTHER
SIR,-The article by Dr Whitelaw and Katharine Sleath (May 25,
1206) does much to put the apparently "miraculous" results of the Bogota home-care programme for low birthweight (LBW) babies into perspective. More importantly, it highlights an innovative attempt to rationalise care of the LBW baby in the developing world. Many medical practices in the Third World have been imported from the developed world with little thought to their suitability. A growing awareness of the inadequacies of the Western medical model to deal with health problems in the developing world underlies the current World Health Organisation emphasis on community based primary health care. About 19 million LBW babies are born in the developing world every year.Most of these will be born in rural areas, and even if the baby is born in hospital the maternity unit is likely to be overcrowded and have only basic facilities for care of the LBW baby. If the baby survives, the unexpectedly prolonged hospital stay will disrupt and cause financial hardship in a subsistence level family already struggling for survival. He may be discharged to a hostile environment and to a family which is much less stable than the one p
in which he was conceived. Such is the situation in Maua Hospital, in rural Kenya, where about 9% of the 4000 babies born each year weigh less than 2500 g. Care of these babies is basic but follows the traditional western model. The babies are nursed in a special nursery, kept warm, fed early with expressed breast milk, and treated with antibiotics if infection is suspected. They are nursed by inexperienced staff, assisted as much as possible by the mothers. There are no incubators or ventilators. In the six months of our study 45 (33-1%) of the LBW babies born died in hospital-16 (89%) of the babies under 1500 g, 15 (58%) of the babies weighing 1500-1999 g, and 14 (15%)