607
Insulin resistance and
cigarette smoking
SiR,—In their comments about our study (June 27, p 1619) of msulin concentrations and insulin resistance in smokers, Dr Reaven and Dr Chen (Aug 8, p 377) question the sensitivity of our method of measuring insulin resistance. These workers previously found a poor correlation between estimates of insulin sensitivity derived with the mathematical modelling procedure we used and the glycaemic clamp. We would point out, however, that their findings relate to a different intravenous glucose tolerance test (IVGTT) procedure from the one we used. The issue here is the magnitude of the IVGTT insulin response and the precision of estimation of insulin sensitivity: there has to be an insulin response of sufficient magnitude for the modelling analysis to return precise estimates of insulin sensivitity. The 0-33 gikg glucose dose used by Reaven and co-workers in their IVGTT comparison study may often fail to elicit an insulin response of sufficient magnitude. Bergman et a 12 have recommended augmentation of the IVGTT insulin response with intravenous tolbutamide (or insulin). With this modification, precise measures of insulin sensitivity have been obtained, and the validity of the modelling analysis confirmed.2 Rather than tolbutamide to augment the IVGTT insulin response, we have used a higher IVGTT glucose dose-0-5 g/kg (as we state in our letter), in preference to 0-3 g/kg. This enables application of other analyses relating to insulin secretion and elimination, and increases the IVGTT insulin response by between 50-100% compared with the lower dose test (D. R. Owens and 1. F. Godsland, unpublished observations). We have found that this higher dose procedure is well able to discriminate significant effects on insulin sensitivity. 3,4 We agree with Reaven and Chen that attention should be paid to the appropriateness of the methods used in investigating insulin resistance, and trust, from their comments, that they agree that modelling analysis of the IVGTT, with an augmented insulin response, is one such. Wynn Institute for Metabolic Research,
IAN F. GODSLAND CHRISTOPHER WALTON
21 Welllington Road, London NW8 9SQ, UK
Youn J, Bergman R. Modified protocols improve insulin sensitivity estimation using the minimal model. Am J Physiol 1987; 253: E595-602. 2 Bergman R, Prager R, Vølund A, Olefsky J. Equivalence of the insulin sensitivity index denved by the minimal model method and the euglycaemic clamp. J Clin Invest 1987, 79: 790-800. 3. Godsland I, Walton C, Felton C, Proudler A, Patel A, Wynn V. Insulin resistance, secretion and metabolism in users of oral contraceptives. J Clin Endocrinol Metab
1. Yang Y,
1992; 74: 64-70. 4. Walton C, Godsland I, Proudler A, Felton C, Wynn V. Evaluation of four mathematical models of glucose and insulin dynamics with analysis of the effects of age and obesity. Am J Physiol 1992; 262: E755-62.
Non-paternity and genetic counselling SIR,-Non-patemity
is
a
delicate
problem
encountered in
genetic counselling, because it is difficult to estimate and may lead
geneticist to the wrong conclusions. Variable rates of nonpaternity, sometimes quite high (up to 30%), have been proposed (for references see Macintyre and Sooman’s papery. In our laboratory, which offers genetic disease diagnosis using molecular biology, we wanted an estimation of the average rate of nonpaternity in the population we serve, so we have tested samples by Southern blot2 or polymerase chain amplification3 using hyperpolymorphic DNA markers corresponding to variable number of tandem repeats (VNTR) .2 We checked 89 files (583 DNAs) corresponding to 50 referrals for Duchenne’s myopathy, 23 cystic fibrosis, 6 haemophilia A or B, and 10 Steinert’s myotony. By "file" we mean the family file set up when a nuclear family is analysed for genetic counselling. We detected 8 non-patemities (9% of files). Most non-paternities (7 of 8) involved only 1 child per family; in one family there were 3 non-paternity
the
children. To estimate, for our population, the rate of children not sired by their declared father we calculated the number of observed non-paternities (10) as a percentage of the meioses (362), "meioses" meaning children in any generation in the families studied. The rate
2-8%, far from the oft-claimed 10%, but close to the results obtained by Edwards (5%)4 and Ashton (2’3%).s A VNTR marker should be analysed in every genetic study since non-patemity can be expected in one-tenth of the files and in one-twentieth of the families. It is also a good control for checking wrongly identified samples or maternal contamination ofchorionic
was
villus samples. MARIE-GAELLE LE ROUX OLIVIER PASCAL MARIE-THERESE ANDRE ODILE HERBERT ALBERT DAVID JEAN-PAUL MOISAN
Molecular Genetics Laboratory and Paediatrics Services, CHRU de Nantes, 44035 Nantes, France 1.
Macintyre S, Sooman A. Non-paternity and prenatal genetic screening. Lancet 1991;
338: 869-71. 2. Nakamura Y, Leppert M, O’Connell P, et al. Variable number of tandem repeat (VNTR) marker for human gene mapping. Science 1987; 235: 1616-22. 3. Budowle B, Chakraborty R, et al. Analysis of the VNTR locus by PCR followed by high-resolution PAGE. Am J Hum Genet 1991; 48: 137-45. 4. Edwards JH. A critical examination of the reputed primary influence of ABO phenotype on fertility and sex ratio. Br J Prev Soc Med 1957; 11: 79-89. 5. Ashton GC. Mismatches in genetic markers m a large family study. Am J Hum Genet 1980; 32: 601-13.
Idiopathic CD4+ T-lymphocytopenia SIR,-Dr Laurence and colleagues (Aug 1, p 273) describe five patients who fulfilled criteria for AIDS or AIDS-related complex, except for HIV-1 or HIV-2 infection. AIDS-defining conditions in the absence of HIV have been reported before. For instance, more than 30 HIV-negative cases of Kaposi’s sarcoma (KS) under 60 of age
years
have
been
described.
However,
none
had
immunodeficiency, CD4 + counts being normal. Earlier this year we described one HIV-negative patient with KS who had disseminated tuberculosis and profound CD4 depletion.1 Similar cases were reported at the Amsterdam AIDS meeting last July, and on Aug 14 the term "idiopathic CD4+ T-lymphocytopenia (ICL)" emerged at a joint CDC/NIH meeting in Atlanta (Aug 22, p 475). A broad spectrum of diseases, infectious and non-infectious, can cause a
fall in CD4 + cell
count:
Infectious diseases: Viral: retroviruses (HIV-1, HIV-2, Adenoviruses
,
HTLV-1)
Herpesviruses (varicella-zoster, HHV-6, CMV) Parvoviruses
Papillomaviruses Measles virus Hepatitis B virus Rickettsial (eg, Rocky Mountain and Mediterranean
spotted fever) Fungal (eg, histoplasmosis, cryptococcosis and coccidiomycosis) Protozoal (eg, leishmaniasis) Bacterial (eg, tuberculosis and brucellosis)
Autoimmune disorders Malnutrition Congenital disorders (eg, partial ADA or PNP deficiencies, associated with hypogammaglobulinaemia and partial DiGeorge
syndrome) Drugs (eg, corticosteroids) Lymphoproliferative disorders, thymoma, intestinal lymphangiectasia, etc Other (eg, old age and pregnancy) A transient fall in CD4 + count seems to be frequent in some infectious diseases. Some depletion may be the result of cytolysis caused by the infectious agent or by cytokines or natural killer cells, for example. However, a fall in peripheral blood CD4 + cell count usually reflects sequestration of CD4 + cells in lymph nodes and the reticuloendothelial system as part of the immune response to infection. Malnutrition, autoimmune diseases, thymoma, and diverse rare congenital disorders have been associated with acquired immunodeficiency, causing CD4 + cell depletion by other mechanisms.2 The US Centers for Disease Control’s working definition for ICL3 should formally exclude several other conditions known to
Insulin resistance and
cigarette smoking
SiR,—In their comments about our study (June 27, p 1619) of msulin concentrations and insulin resistance in smokers, Dr Reaven and Dr Chen (Aug 8, p 377) question the sensitivity of our method of measuring insulin resistance. These workers previously found a poor correlation between estimates of insulin sensitivity derived with the mathematical modelling procedure we used and the glycaemic clamp. We would point out, however, that their findings relate to a different intravenous glucose tolerance test (IVGTT) procedure from the one we used. The issue here is the magnitude of the IVGTT insulin response and the precision of estimation of insulin sensitivity: there has to be an insulin response of sufficient magnitude for the modelling analysis to return precise estimates of insulin sensivitity. The 0-33 gikg glucose dose used by Reaven and co-workers in their IVGTT comparison study may often fail to elicit an insulin response of sufficient magnitude. Bergman et a 12 have recommended augmentation of the IVGTT insulin response with intravenous tolbutamide (or insulin). With this modification, precise measures of insulin sensitivity have been obtained, and the validity of the modelling analysis confirmed.2 Rather than tolbutamide to augment the IVGTT insulin response, we have used a higher IVGTT glucose dose-0-5 g/kg (as we state in our letter), in preference to 0-3 g/kg. This enables application of other analyses relating to insulin secretion and elimination, and increases the IVGTT insulin response by between 50-100% compared with the lower dose test (D. R. Owens and 1. F. Godsland, unpublished observations). We have found that this higher dose procedure is well able to discriminate significant effects on insulin sensitivity. 3,4 We agree with Reaven and Chen that attention should be paid to the appropriateness of the methods used in investigating insulin resistance, and trust, from their comments, that they agree that modelling analysis of the IVGTT, with an augmented insulin response, is one such. Wynn Institute for Metabolic Research,
IAN F. GODSLAND CHRISTOPHER WALTON
21 Welllington Road, London NW8 9SQ, UK
Youn J, Bergman R. Modified protocols improve insulin sensitivity estimation using the minimal model. Am J Physiol 1987; 253: E595-602. 2 Bergman R, Prager R, Vølund A, Olefsky J. Equivalence of the insulin sensitivity index denved by the minimal model method and the euglycaemic clamp. J Clin Invest 1987, 79: 790-800. 3. Godsland I, Walton C, Felton C, Proudler A, Patel A, Wynn V. Insulin resistance, secretion and metabolism in users of oral contraceptives. J Clin Endocrinol Metab
1. Yang Y,
1992; 74: 64-70. 4. Walton C, Godsland I, Proudler A, Felton C, Wynn V. Evaluation of four mathematical models of glucose and insulin dynamics with analysis of the effects of age and obesity. Am J Physiol 1992; 262: E755-62.
Non-paternity and genetic counselling SIR,-Non-patemity
is
a
delicate
problem
encountered in
genetic counselling, because it is difficult to estimate and may lead
geneticist to the wrong conclusions. Variable rates of nonpaternity, sometimes quite high (up to 30%), have been proposed (for references see Macintyre and Sooman’s papery. In our laboratory, which offers genetic disease diagnosis using molecular biology, we wanted an estimation of the average rate of nonpaternity in the population we serve, so we have tested samples by Southern blot2 or polymerase chain amplification3 using hyperpolymorphic DNA markers corresponding to variable number of tandem repeats (VNTR) .2 We checked 89 files (583 DNAs) corresponding to 50 referrals for Duchenne’s myopathy, 23 cystic fibrosis, 6 haemophilia A or B, and 10 Steinert’s myotony. By "file" we mean the family file set up when a nuclear family is analysed for genetic counselling. We detected 8 non-patemities (9% of files). Most non-paternities (7 of 8) involved only 1 child per family; in one family there were 3 non-paternity
the
children. To estimate, for our population, the rate of children not sired by their declared father we calculated the number of observed non-paternities (10) as a percentage of the meioses (362), "meioses" meaning children in any generation in the families studied. The rate
2-8%, far from the oft-claimed 10%, but close to the results obtained by Edwards (5%)4 and Ashton (2’3%).s A VNTR marker should be analysed in every genetic study since non-patemity can be expected in one-tenth of the files and in one-twentieth of the families. It is also a good control for checking wrongly identified samples or maternal contamination ofchorionic
was
villus samples. MARIE-GAELLE LE ROUX OLIVIER PASCAL MARIE-THERESE ANDRE ODILE HERBERT ALBERT DAVID JEAN-PAUL MOISAN
Molecular Genetics Laboratory and Paediatrics Services, CHRU de Nantes, 44035 Nantes, France 1.
Macintyre S, Sooman A. Non-paternity and prenatal genetic screening. Lancet 1991;
338: 869-71. 2. Nakamura Y, Leppert M, O’Connell P, et al. Variable number of tandem repeat (VNTR) marker for human gene mapping. Science 1987; 235: 1616-22. 3. Budowle B, Chakraborty R, et al. Analysis of the VNTR locus by PCR followed by high-resolution PAGE. Am J Hum Genet 1991; 48: 137-45. 4. Edwards JH. A critical examination of the reputed primary influence of ABO phenotype on fertility and sex ratio. Br J Prev Soc Med 1957; 11: 79-89. 5. Ashton GC. Mismatches in genetic markers m a large family study. Am J Hum Genet 1980; 32: 601-13.
Idiopathic CD4+ T-lymphocytopenia SIR,-Dr Laurence and colleagues (Aug 1, p 273) describe five patients who fulfilled criteria for AIDS or AIDS-related complex, except for HIV-1 or HIV-2 infection. AIDS-defining conditions in the absence of HIV have been reported before. For instance, more than 30 HIV-negative cases of Kaposi’s sarcoma (KS) under 60 of age
years
have
been
described.
However,
none
had
immunodeficiency, CD4 + counts being normal. Earlier this year we described one HIV-negative patient with KS who had disseminated tuberculosis and profound CD4 depletion.1 Similar cases were reported at the Amsterdam AIDS meeting last July, and on Aug 14 the term "idiopathic CD4+ T-lymphocytopenia (ICL)" emerged at a joint CDC/NIH meeting in Atlanta (Aug 22, p 475). A broad spectrum of diseases, infectious and non-infectious, can cause a
fall in CD4 + cell
count:
Infectious diseases: Viral: retroviruses (HIV-1, HIV-2, Adenoviruses
,
HTLV-1)
Herpesviruses (varicella-zoster, HHV-6, CMV) Parvoviruses
Papillomaviruses Measles virus Hepatitis B virus Rickettsial (eg, Rocky Mountain and Mediterranean
spotted fever) Fungal (eg, histoplasmosis, cryptococcosis and coccidiomycosis) Protozoal (eg, leishmaniasis) Bacterial (eg, tuberculosis and brucellosis)
Autoimmune disorders Malnutrition Congenital disorders (eg, partial ADA or PNP deficiencies, associated with hypogammaglobulinaemia and partial DiGeorge
syndrome) Drugs (eg, corticosteroids) Lymphoproliferative disorders, thymoma, intestinal lymphangiectasia, etc Other (eg, old age and pregnancy) A transient fall in CD4 + count seems to be frequent in some infectious diseases. Some depletion may be the result of cytolysis caused by the infectious agent or by cytokines or natural killer cells, for example. However, a fall in peripheral blood CD4 + cell count usually reflects sequestration of CD4 + cells in lymph nodes and the reticuloendothelial system as part of the immune response to infection. Malnutrition, autoimmune diseases, thymoma, and diverse rare congenital disorders have been associated with acquired immunodeficiency, causing CD4 + cell depletion by other mechanisms.2 The US Centers for Disease Control’s working definition for ICL3 should formally exclude several other conditions known to
