1036 The "real false-positive". Either the media are not able to sustain growth with few organisms not visible by z.N., or the organisms seen with auramine are artefacts.
EVOLUTION OF X-CHROMOSOME INACTIVATION
SIR,-Dr Hoo’ says that deletion of the short arm of the human X chromosome not involving segment b of his figure (corresponding to Xpll of the Paris Nomenclature) does not cause any clinical symptoms. From this he concludes that segment a (corresponding to Xp2 and part of Xpl) is present fourfold in the female. He cites a case reported on at the meeting of the German Cytogenetical Society2 with a short-arm deletion at band pll in a mother and daughter, both of whom apparently were without any clinical manifestations. Dr Hoo seems to be unaware of a case published by Boczkowski and Mikkelsen3 with a similar X short-arm deletion at band pll, who showed signs of Turner’s syndrome, including primary amenorrhcea, short stature, and webbing of the neck. It follows that segment a may not be present four-fold, as Dr Hoo suggests, and therefore that his theory of sex-chromosome evolution may not be correct. Institute of Genetics, Basle University Children’s Hospital, CH-4000 Basle, Switzerland.
carefully at the morphology In our experience, some of these particles. found when blood is have been auramine stains false-positive The in the morphology of these fluorescent present sputum. particles is sometimes difficult to evaluate. Some of them are platelets (which stain with auramine). If there is gross contamination with blood, there is no problem in identifying the probable cause of the false-positive smear. If there is occult blood in the sputum, there is the possibility of false-positive auramine stain, and the z.N. will be negative. We are now investigating the auramine staining of artificially platelet-contaminated sputum in order to evaluate the extent of the falsepositive auramine staining. Also, we use it to train technicians to look more carefully at the morphology of the fluorescent In the last case, of the fluorescent
should look
particles. Brown
University, Hospital,
Memorial
Pawtucket, Rhode Island 02860,
E. M. BÜHLER
F. P. ROLAND
U.S.A
FALSE-POSITIVE ACID-FAST SMEARS
StR,-As
one
B.C.G. AT SCHOOL
Dr Weinstein and his
colleagues say (July 26, 173), "ongoing analysis" of sputum specimens is essential for early detection of smears false-positive for mycobacteria. False-positive smears are smear-positive, culture-negative spe-
are concerned about the implications of your edi(Sept. 27, p. 593), suggesting that tuberculosis is now disappearing to such an extent that one can afford to be complacent. The reasons for abandoning the routine tuberculin testing of 13-year-old schoolchildren and giving B.c.G. are, firstly, that an insignificant number of children are picked up
SIR,-We
torial
p.
cimens. One
must distinguish between the false-positive due to laboratory contamination and the smears that Dr Mitchison and her colleagues (Aug. 9, p. 281) call the "genuine falsepositive", where no reasons are found for failure of growth after a positive smear. The interpretation by the clinician of these positive smears is extremely difficult. This is even more important with auramine staining of sputum,’ which is easier to perform and read and more sensitive than the Ziehl-Neelsen (z.N.). Does the finding of a positive auramine stain alone, in patients not on chemotherapy, warrant starting antituberculous therapy without waiting for the results of the culture? More data on the follow-up of patients with positive smears only should be made available. The decision to treat or not to treat has to be made at the time of the smear. Retrospective
studies, which include the results of the cultures, have
no
with tuberculous infection relative to the expense and work involved, and, secondly, that the incidence of tuberculosis is now so low that there is no need to protect the population, Tuberculosis has definitely not disappeared. Amongst 13-year-olds Heaf-tested in North Hampshire in the past two academic years, 47 were found to have strongly positive reactions ; and, of these, 4 had active tuberculosis. 2 of the children had primary infections which had ulcerated into the bronchial wall and were therefore infectious. As these 4 all came from different comprehensive schools, with the number of pupils varying from 1087 to 1435, this involved a large amount of additional screening with serious public-health implications. In the past year, from the town of Alton (population 13 800), there have been 23 cases of tuberculosis notified. 13 of these were from the same source; 3 adults had active tuberculosis; 10 children were found to have primary infections, and 7 of these are now receiving treatment. Of the further 10 additional cases, only 2 men who work in the same business have had any known contact with each other. Amongst the 5 children in this group, 2 have extrapulmonary infections; and, among the children in Alton receiving treatment, 6 are 6 years of age or younger. We are not convinced that tuberculosis has been conquered, and we cannot therefore, afford to be complacent about this potentially serious disease. J. C. BOWE Basingstoke District Hospital, J. M. DARMADY Park Prewett, T. E. ROBERTS Basingstoke, P. TOMLINSON Hants RG24 9NA
value
far as treatment is concerned. This laboratory follows the procedures of the Communicable Disease Center, Atlanta, Georgia. The sputum is stained with auramine, and only the positives are stained with Z.N. All specimens are cultured. In three years, 4669 specimens have been processed. The positives results can be classified in five as
categories.
-
Category 1.-Stain-negative, culture-positive. This is why cultures done. Specimens are negative to both stains, probably because there are too few mycobacteria to be picked up. Category 2.-All positive. Enough bacteria to be picked up by both are
-
-_
stains.
Category 3.-Auramine-positive, z.N.-negative, with a positive culDemonstrates the advantage of the auramine stain. Category 4.--Positive with both stains, culture negative. Either the bacteria were not viable or the media were inadequate to support their growth. Culture media do not sustain growth as well as the lungs do. Category 5.-Auramine-positive, z.N.-neganve, culture-negative.
ture.
1. Hoo, J.-J. Lancet, 1975, i, 1299. 2. Van den Berghe, H. Meeting of the German Cytogenetical Society Berlin, 1974. 3. Boczkowski, K., Mikkelsen, M. J. med. Genet. 1973, 10, 350. 4 Bennedsen, J, Larsen, S. O. Scand. J. resp. Dis. 1966, 47, 114.
WITHDRAWAL OF CORTICOSTEROIDS ,
SIR,-How should corticosteroids be withdrawn from a patient maintained on them? You say in your editorial (Sept. 20, p. 537) that 1 mg prednisone or its equivalent should be withdrawn about every three days. Dr Bloom (Oct. 4, p. 659) thinks this is too quick; and Grant’ would withdraw only 1 mg per month. Naturally, withdrawal should be gradual, since we assume 1. Grant, I. W. B. Prescribers
J. 1975, 15, 46.
EVOLUTION OF X-CHROMOSOME INACTIVATION
SIR,-Dr Hoo’ says that deletion of the short arm of the human X chromosome not involving segment b of his figure (corresponding to Xpll of the Paris Nomenclature) does not cause any clinical symptoms. From this he concludes that segment a (corresponding to Xp2 and part of Xpl) is present fourfold in the female. He cites a case reported on at the meeting of the German Cytogenetical Society2 with a short-arm deletion at band pll in a mother and daughter, both of whom apparently were without any clinical manifestations. Dr Hoo seems to be unaware of a case published by Boczkowski and Mikkelsen3 with a similar X short-arm deletion at band pll, who showed signs of Turner’s syndrome, including primary amenorrhcea, short stature, and webbing of the neck. It follows that segment a may not be present four-fold, as Dr Hoo suggests, and therefore that his theory of sex-chromosome evolution may not be correct. Institute of Genetics, Basle University Children’s Hospital, CH-4000 Basle, Switzerland.
carefully at the morphology In our experience, some of these particles. found when blood is have been auramine stains false-positive The in the morphology of these fluorescent present sputum. particles is sometimes difficult to evaluate. Some of them are platelets (which stain with auramine). If there is gross contamination with blood, there is no problem in identifying the probable cause of the false-positive smear. If there is occult blood in the sputum, there is the possibility of false-positive auramine stain, and the z.N. will be negative. We are now investigating the auramine staining of artificially platelet-contaminated sputum in order to evaluate the extent of the falsepositive auramine staining. Also, we use it to train technicians to look more carefully at the morphology of the fluorescent In the last case, of the fluorescent
should look
particles. Brown
University, Hospital,
Memorial
Pawtucket, Rhode Island 02860,
E. M. BÜHLER
F. P. ROLAND
U.S.A
FALSE-POSITIVE ACID-FAST SMEARS
StR,-As
one
B.C.G. AT SCHOOL
Dr Weinstein and his
colleagues say (July 26, 173), "ongoing analysis" of sputum specimens is essential for early detection of smears false-positive for mycobacteria. False-positive smears are smear-positive, culture-negative spe-
are concerned about the implications of your edi(Sept. 27, p. 593), suggesting that tuberculosis is now disappearing to such an extent that one can afford to be complacent. The reasons for abandoning the routine tuberculin testing of 13-year-old schoolchildren and giving B.c.G. are, firstly, that an insignificant number of children are picked up
SIR,-We
torial
p.
cimens. One
must distinguish between the false-positive due to laboratory contamination and the smears that Dr Mitchison and her colleagues (Aug. 9, p. 281) call the "genuine falsepositive", where no reasons are found for failure of growth after a positive smear. The interpretation by the clinician of these positive smears is extremely difficult. This is even more important with auramine staining of sputum,’ which is easier to perform and read and more sensitive than the Ziehl-Neelsen (z.N.). Does the finding of a positive auramine stain alone, in patients not on chemotherapy, warrant starting antituberculous therapy without waiting for the results of the culture? More data on the follow-up of patients with positive smears only should be made available. The decision to treat or not to treat has to be made at the time of the smear. Retrospective
studies, which include the results of the cultures, have
no
with tuberculous infection relative to the expense and work involved, and, secondly, that the incidence of tuberculosis is now so low that there is no need to protect the population, Tuberculosis has definitely not disappeared. Amongst 13-year-olds Heaf-tested in North Hampshire in the past two academic years, 47 were found to have strongly positive reactions ; and, of these, 4 had active tuberculosis. 2 of the children had primary infections which had ulcerated into the bronchial wall and were therefore infectious. As these 4 all came from different comprehensive schools, with the number of pupils varying from 1087 to 1435, this involved a large amount of additional screening with serious public-health implications. In the past year, from the town of Alton (population 13 800), there have been 23 cases of tuberculosis notified. 13 of these were from the same source; 3 adults had active tuberculosis; 10 children were found to have primary infections, and 7 of these are now receiving treatment. Of the further 10 additional cases, only 2 men who work in the same business have had any known contact with each other. Amongst the 5 children in this group, 2 have extrapulmonary infections; and, among the children in Alton receiving treatment, 6 are 6 years of age or younger. We are not convinced that tuberculosis has been conquered, and we cannot therefore, afford to be complacent about this potentially serious disease. J. C. BOWE Basingstoke District Hospital, J. M. DARMADY Park Prewett, T. E. ROBERTS Basingstoke, P. TOMLINSON Hants RG24 9NA
value
far as treatment is concerned. This laboratory follows the procedures of the Communicable Disease Center, Atlanta, Georgia. The sputum is stained with auramine, and only the positives are stained with Z.N. All specimens are cultured. In three years, 4669 specimens have been processed. The positives results can be classified in five as
categories.
-
Category 1.-Stain-negative, culture-positive. This is why cultures done. Specimens are negative to both stains, probably because there are too few mycobacteria to be picked up. Category 2.-All positive. Enough bacteria to be picked up by both are
-
-_
stains.
Category 3.-Auramine-positive, z.N.-negative, with a positive culDemonstrates the advantage of the auramine stain. Category 4.--Positive with both stains, culture negative. Either the bacteria were not viable or the media were inadequate to support their growth. Culture media do not sustain growth as well as the lungs do. Category 5.-Auramine-positive, z.N.-neganve, culture-negative.
ture.
1. Hoo, J.-J. Lancet, 1975, i, 1299. 2. Van den Berghe, H. Meeting of the German Cytogenetical Society Berlin, 1974. 3. Boczkowski, K., Mikkelsen, M. J. med. Genet. 1973, 10, 350. 4 Bennedsen, J, Larsen, S. O. Scand. J. resp. Dis. 1966, 47, 114.
WITHDRAWAL OF CORTICOSTEROIDS ,
SIR,-How should corticosteroids be withdrawn from a patient maintained on them? You say in your editorial (Sept. 20, p. 537) that 1 mg prednisone or its equivalent should be withdrawn about every three days. Dr Bloom (Oct. 4, p. 659) thinks this is too quick; and Grant’ would withdraw only 1 mg per month. Naturally, withdrawal should be gradual, since we assume 1. Grant, I. W. B. Prescribers
J. 1975, 15, 46.
