- Email: [email protected]
Pneumocystis carinii genotypes and severity of pneumonia
This atraumatic method of puncturing the dura has been primarily developed in the field of anaesthetics and epidurals and awareness of this advance is not widespread in certain groups who regularly perform lumbar punctures (neurologists, neurosurgeons, haematologists, and medical oncologists). The use of atraumatic lumbar puncture needles results in a marked reduction in the morbidity associated with intrathecal chemotherapy. 1
Kuntz KM, Kokmen E, Stevens JC, Miller P, Offord KP, Ho MM. Post lumbar puncture headaches: experience in 501 consecutive procedures. Neurology 1992; 42: 1884–87. 2 Tohmo H, Vuorinen E, Muuronen A. Prolonged impairment in activities of daily livng due to postdural puncture. Anaethesia 1998; 53: 299–302. 3 Serpell MG, Haldane GJ, Jamieson DRS, Carson D. Prevention of headache after lumbar puncture: questionnaire survey of neurologists and neurosurgeons in the United Kingdom. BMJ 1998; 3 1 6 : 1709–10. 4 Broadley SA, Fuller GA. Lumbar puncture needn’t be a headache. BMJ 1997; 315: 1324–25. 5 Broadley SA, Fuller GN. Audit of lumbar puncture practice in United Kingdom neurology centres. J Neurol Neurosurg Psychiatry 1997; 63: 266.
Department of Medical Oncology, Charing Cross Hospital, Fulham Palace Road, London W6 8RF, UK (E S Newlands)
The increasing frequency with which enterohaemorrhagic Escherichia coli (EHEC) are isolated from the faeces of patients has led to concern among clinicians and publichealth officials. Although the main infection routes are person-to-person contact and consumption of undercooked meat or raw milk,1 other modes of transmission have to be kept in mind. Sewage discharge into water used for recreational purposes might endanger many people, especially children. We sampled inflow and outflow of sewage-treatment plants in northern Germany during the summer months of 1998. After centrifugation and selective enrichment the samples were screened with a seminested PCR, after an immunomagnetic separation for the presence of the virulence genes for Shiga-like toxins (SLT) I and II, intimin, and haemolysin (eaeA and hly). SLT I or II-positive-PCR samples were examined by colony immunoblot. 2 Presumptive E coli colonies were isolated, differentiated biochemically, counterchecked for the presence of the virulence genes, and serotyped. 29 (93%) samples were either SLT I-positive or II-positive in the first PCR (table) and 35% of these samples showed a positive reaction in the colony immunoblot. Five E coli strains could be isolated where the second PCR, done as a countercheck, resulted in SLT I or II-positive reactions. One strain (EHEC 0157:H7) originated from the inflow of a sewage plant with 55 000 population equivalents, the four other strains were non-typable, rough strains from the
Inflow Outflow
16 15
Bockemühl J, Karch H. Zur aktuellen Bedeutung der enterohämorrhagischen Escherichia coli (EHEC) in Deutschland (1994–1995). Bundesgesundh bl 1996; 39: 290–96. 2 Timm M, Klie H, Richter H, Perlberg K-W. Eine Methode zur gezielten Isolierung Verotoxin-bildender Escherichia coli-Kolonien. Berl Münch Tierärzl Wschr 1996; 109: 270–72. 3 Grant SR, Pendroy CP, Mayer CL, Bellin JK, Palmer CJ. Prevalence of enterohemorrhagic Escherichia coli in raw and treated municipal sewage. Appl Environ Microbiol 1996; 62: 3466–69. Institute for Hygiene and Environmental Medicine, University of Kiel, Brunswiker Str 4, D-24105 Kiel, Germany (C Höller e-mail: [email protected])
Robert F Miller, Ann E Wakefield
Christiane Höller, Susann Koschinsky, Doris Witthuhn
No of samples screened
1
Pneumocystis carinii genotypes and severity of pneumonia
Isolation of enterohaemorrhagic Escherichia coli from municipal sewage
Sewage treatment plant
outflow of plants with population equivalents of 750 000, 380 000, and 55 000, after tertiary treatment. To our knowledge this is the first report of isolation of EHEC from municipal sewage. Although only five strains with the virulence genes were subcultured from the colony immunoblot plates, we feel that further modification of the method to overcome the heavy overgrowth will show a higher rate of isolation. In a study by Grant et al,3 only one influent and no effluent samples had been SLT II-DNA positive and no SLT-positive strains were detected, leading the authors to reject a possible public health hazard. Based on the results of our preliminary study a reconsideration of the situation is necessary.
Pneumocystis carinii pneumonia (PCP) is an important cause of respiratory morbidity in immunosuppressed patients. Presentation varies from mild pneumonia, with only minor chest radiographic abnormalities with normal or near normal arterial blood gases, to severe pneumonia with marked radiographic abnormalities and hypoxaemia. 1 Several criteria have been used to assess the severity of P carinii pneumonia; the most widely used is the arterial oxygen tension (PaO2) breathing air, values of less than 9·3 kPa indicating the need for adjuvant glucocorticoids.1 Other severity criteria include the degree of radiographic abnormalities, presence of pulmonary co-pathology, and elevation of lactate dehydrogenase enzyme concentrations.1 Because it is not possible to culture human-derived P carinii, many typing methods for distinguishing between different isolates are not available. Molecular techniques have shown diversity amongst isolates of human-derived P carinii by comparison of DNA-sequence variation at a number of different genetic loci, the internal transcribed spacer (ITS) regions of the nuclear ribosomal RNA operon begin the most informative.2–4 As yet there are no data to show that severity of PCP may be related to specific genotypes of P carinii. 30 HIV-infected patients with PCP were studied prospectively. In 26, the episode of PCP was their first (3 of these subsequently had one repeat episode and 5 had two repeat episodes) and in four patients the second episode of PCP was studied, resulting in a total of 43 episodes being analysed. PCP was diagnosed bronchoscopically in 41 samples and from induced sputum in two samples. 21 different ITS sequence types were found. In 32 episodes, a single ITS sequence type was identified and in 11 episodes,
First PCR
Immunoblot
SLT I
SLT II
eaeA
hly
62 (10) 73 (11)
075% (12) 100% (15)
87% (14) 80% (12)
81% (13) 93% (14)
31% (5) 40% (6)
Second PCR SLT I
SLT II
06% (1) 13% (2)
06% (1) 27% (4)
Percentage of positive sewage samples
THE LANCET • Vol 353 • June 12, 1999
2039
Disease severity Moderate/severe
Mild
PaO2* Number of patients
<9·3 15
>9·3 11
Genotypes
B2a1, B 2d1, A 4a3 B1a3 B1a3 B1 a3, B1c1 B1a3, Ca3 B1b1
B2 a1 B2a1 B2 a1, B2a2 B2a1, B 1d1 B2a1 B2a1 , B1a1, B 1a3, B1e1 , B1e2, B1e3, B2 a2, B2a3, B2a3, B3 a3 B2a3, B 1a2, B2 a3, B1a3, B4a3, B1 a1 B1a3 B1b1 B1b2 B1f
B1b1 B1b1, B1 b2 B1d1† B2a5 A2c1 A2c1 A2c1 A4a3 Ca3 † Clinical variables Duration of symptoms (weeks) Use of primary prophylaxis CD4 lymphocyte count (cells/L) Pulmonary co-pathology
1–8 (2) 4 10–310 (60) 1
1–3 (2) 6 10–100 (65) 3
Data are range (median). Key: *kPa, breathing room air. †Patient died.
P carinii ITS sequence types and clinical variables in first episode PCP
more than one type was found, indicative of a mixed infection. The 26 patients with a first episode of PCP were divided into two groups based on their arterial oxygen tension on admission and the need for adjuvant glucocorticoids (table). The two groups were similar in their clinical presentation, CD4 lymphocyte count, use of primary prophylaxis, and presence of pulmonary co-pathogens. ITS type B2a1 was the most frequently identified, in eight patients of whom seven had mild disease, B1a3 was found in seven patients (4 with moderate/severe disease) and type A2c1 was found only in moderate/severe disease. Of 17 episodes of second or third episodes of PCP, four were moderate/severe and 13 were mild. Analysis was confounded by prior administration of anti-P carinii treatment and prophylaxis. However there was still an association of ITS sequence type B2a1 with mild disease, 19/24 (mild) compared with 4/19 (moderate/severe). Type B1a3 was found only in first and not in subsequent episodes of PCP. In contrast, ITS sequence type B2a1, the most common type in this study (and also in other studies4) was the most frequently identified in samples from second and third episodes, and may represent a more persistent or transmissible genotype of human-derived P carinii. These data suggest that in addition to host factors, the severity of PCP may also be associated wtih ITS sequence type of P carinii. This methodology may be applied to noninvasive samples such as oropharyngeal washes,5 and might be used in clinical practice to provide additional data on which to base treatment decisions, especially use of adjuvant glucocorticoids, and identification of patients requring inpatient-based treatment of PCP. We thank Anthony G Tsolaki for sequence data. 1
National Institutes of Health, University of California Expert Panel for Corticosteroids as Adjunctive Threapy for Pneumocystis Pneumonia Consensus statement on the use of corticosteroids as adjunctive therapy for Pneumocystis pneumonia in the acquired immunodeficiency syndrome. N Engl J Med 1990; 323: 1500–04. 2 Lu J-J, Bartlett MS, Shaw MM, et al. Typing of Pneumocystis carinii strains that infect humans based on nucleotide sequence variations of intenal transcribed spacers of rRNA genes. J Clin Microbiol 1994; 32: 2904–12. 3 Tsolaki AG, Miller RF, Underwood AP, Banerji S, Wakefield AE. Genetic diversity at the internal transcribed spacer regions of the rRNA operon among isolates of Pneumocystis carinii from AIDS
2040
patients with recurrent pneumonia. J Infect Dis 1996; 174: 141–56. 4 Lee C-H, Helweg-Larsen J, Tang X, et al. Update on Pneumocystis carinii f. sp. hominis typing based on nucleotide sequence variations in internal transcribed spacer regions of rRNA genes. J Clin Microbiol 1998; 36: 734–41. 5 Tsolaki AG, Miller RF, Wakefield AE. Oropharyngeal samples for genotyping and monitoring of response to treatment of Pneumocystis carinii in persons with AIDS. J Med Microbiol (in press). Department of Sexually Transmitted Diseases, Windeyer Institute of Medical Sciences, Royal Free and University College Medical School, London WC1E 6AU, UK (R F Miller e-mail: [email protected]) and Molecular Infectious Diseases Group, Department of Paediatrics, Institute of Molecular Medicine, Oxford
Intake of trans fatty acids and prevalence of childhood asthma and allergies in Europe Stephan K Weiland, Erika von Mutius, Anika Hüsing, M Innes Asher, on behalf of the ISAAC Steering Committee
Intake of certain polyunsaturated fatty acids, particularly n3 and n-6 fatty acids, has been associated with the development of asthma and allergies in children, but little is known whether the configuration (cis or trans) of these fatty acids plays a role. We investigated the association between intake of trans fatty acids and the prevalence of childhood asthma and allergies in ten European countries. Detailed data on the intake of trans fatty acids and other fatty acids in 14 European countries have recently been provided by a collaborative study that used representative market baskets per country.1 Trans fatty acids occur in dairy products, fat of ruminant animals, and industrially hydrogenated vegetable fats (such as margarine). The International Study of Asthma and Allergies in Childhood (ISAAC) has studied the prevalence of asthma, allergic rhinoconjunctivitis, and atopic eczema in children aged 13–14 years in 155 centres around the world using standardised written and video questionnaires.2 Prevalence estimates were available for 55 study centres in ten countries with data on fatty acid intake: Belgium (1 study centre), Finland (4), France (5), Germany (2), Greece (1), Italy (13), Portugal (4), Spain (8), Sweden (2), UK (15). Linear regression analysis was used to assess the association between the 12-month prevalence of symptoms of asthma (wheeze), allergic rhinoconjunctivitis (runny nose with itchy eyes), and atopic eczema (flexural dermatitis) in those aged 13–14 years and the intake of fatty acids using the country estimate for all centres in the respective countries. There was a positive association between the intake of trans fatty acids (expressed as percent of energy intake) and the prevalence of symptoms of asthma, allergic rhinoconjunctivitis, and atopic eczema (figure). After adjustment for gross national product of the country all these associations remained statistically significant (p<0·001), as was the association with the prevalence of asthma symptoms during the last year assessed by the video questionnaire (p<0·05, data not shown). The associations tended to be stronger when the analyses were restricted to estimates of trans fatty acid intake from sources that contain predominantly hydrogenated vegetable fat, such as oils, biscuits, cakes, and chips.1 Similarly consistent associations were not seen for intake of monounsaturated or polyunsaturated fatty acids in cis configuration. Ecological studies allow comparison of populations with large differences in exposures, but an observed association between populations does not necessarily exist also between individuals. The estimates of trans fatty acid intake
THE LANCET • Vol 353 • June 12, 1999
Kuntz KM, Kokmen E, Stevens JC, Miller P, Offord KP, Ho MM. Post lumbar puncture headaches: experience in 501 consecutive procedures. Neurology 1992; 42: 1884–87. 2 Tohmo H, Vuorinen E, Muuronen A. Prolonged impairment in activities of daily livng due to postdural puncture. Anaethesia 1998; 53: 299–302. 3 Serpell MG, Haldane GJ, Jamieson DRS, Carson D. Prevention of headache after lumbar puncture: questionnaire survey of neurologists and neurosurgeons in the United Kingdom. BMJ 1998; 3 1 6 : 1709–10. 4 Broadley SA, Fuller GA. Lumbar puncture needn’t be a headache. BMJ 1997; 315: 1324–25. 5 Broadley SA, Fuller GN. Audit of lumbar puncture practice in United Kingdom neurology centres. J Neurol Neurosurg Psychiatry 1997; 63: 266.
Department of Medical Oncology, Charing Cross Hospital, Fulham Palace Road, London W6 8RF, UK (E S Newlands)
The increasing frequency with which enterohaemorrhagic Escherichia coli (EHEC) are isolated from the faeces of patients has led to concern among clinicians and publichealth officials. Although the main infection routes are person-to-person contact and consumption of undercooked meat or raw milk,1 other modes of transmission have to be kept in mind. Sewage discharge into water used for recreational purposes might endanger many people, especially children. We sampled inflow and outflow of sewage-treatment plants in northern Germany during the summer months of 1998. After centrifugation and selective enrichment the samples were screened with a seminested PCR, after an immunomagnetic separation for the presence of the virulence genes for Shiga-like toxins (SLT) I and II, intimin, and haemolysin (eaeA and hly). SLT I or II-positive-PCR samples were examined by colony immunoblot. 2 Presumptive E coli colonies were isolated, differentiated biochemically, counterchecked for the presence of the virulence genes, and serotyped. 29 (93%) samples were either SLT I-positive or II-positive in the first PCR (table) and 35% of these samples showed a positive reaction in the colony immunoblot. Five E coli strains could be isolated where the second PCR, done as a countercheck, resulted in SLT I or II-positive reactions. One strain (EHEC 0157:H7) originated from the inflow of a sewage plant with 55 000 population equivalents, the four other strains were non-typable, rough strains from the
Inflow Outflow
16 15
Bockemühl J, Karch H. Zur aktuellen Bedeutung der enterohämorrhagischen Escherichia coli (EHEC) in Deutschland (1994–1995). Bundesgesundh bl 1996; 39: 290–96. 2 Timm M, Klie H, Richter H, Perlberg K-W. Eine Methode zur gezielten Isolierung Verotoxin-bildender Escherichia coli-Kolonien. Berl Münch Tierärzl Wschr 1996; 109: 270–72. 3 Grant SR, Pendroy CP, Mayer CL, Bellin JK, Palmer CJ. Prevalence of enterohemorrhagic Escherichia coli in raw and treated municipal sewage. Appl Environ Microbiol 1996; 62: 3466–69. Institute for Hygiene and Environmental Medicine, University of Kiel, Brunswiker Str 4, D-24105 Kiel, Germany (C Höller e-mail: [email protected])
Robert F Miller, Ann E Wakefield
Christiane Höller, Susann Koschinsky, Doris Witthuhn
No of samples screened
1
Pneumocystis carinii genotypes and severity of pneumonia
Isolation of enterohaemorrhagic Escherichia coli from municipal sewage
Sewage treatment plant
outflow of plants with population equivalents of 750 000, 380 000, and 55 000, after tertiary treatment. To our knowledge this is the first report of isolation of EHEC from municipal sewage. Although only five strains with the virulence genes were subcultured from the colony immunoblot plates, we feel that further modification of the method to overcome the heavy overgrowth will show a higher rate of isolation. In a study by Grant et al,3 only one influent and no effluent samples had been SLT II-DNA positive and no SLT-positive strains were detected, leading the authors to reject a possible public health hazard. Based on the results of our preliminary study a reconsideration of the situation is necessary.
Pneumocystis carinii pneumonia (PCP) is an important cause of respiratory morbidity in immunosuppressed patients. Presentation varies from mild pneumonia, with only minor chest radiographic abnormalities with normal or near normal arterial blood gases, to severe pneumonia with marked radiographic abnormalities and hypoxaemia. 1 Several criteria have been used to assess the severity of P carinii pneumonia; the most widely used is the arterial oxygen tension (PaO2) breathing air, values of less than 9·3 kPa indicating the need for adjuvant glucocorticoids.1 Other severity criteria include the degree of radiographic abnormalities, presence of pulmonary co-pathology, and elevation of lactate dehydrogenase enzyme concentrations.1 Because it is not possible to culture human-derived P carinii, many typing methods for distinguishing between different isolates are not available. Molecular techniques have shown diversity amongst isolates of human-derived P carinii by comparison of DNA-sequence variation at a number of different genetic loci, the internal transcribed spacer (ITS) regions of the nuclear ribosomal RNA operon begin the most informative.2–4 As yet there are no data to show that severity of PCP may be related to specific genotypes of P carinii. 30 HIV-infected patients with PCP were studied prospectively. In 26, the episode of PCP was their first (3 of these subsequently had one repeat episode and 5 had two repeat episodes) and in four patients the second episode of PCP was studied, resulting in a total of 43 episodes being analysed. PCP was diagnosed bronchoscopically in 41 samples and from induced sputum in two samples. 21 different ITS sequence types were found. In 32 episodes, a single ITS sequence type was identified and in 11 episodes,
First PCR
Immunoblot
SLT I
SLT II
eaeA
hly
62 (10) 73 (11)
075% (12) 100% (15)
87% (14) 80% (12)
81% (13) 93% (14)
31% (5) 40% (6)
Second PCR SLT I
SLT II
06% (1) 13% (2)
06% (1) 27% (4)
Percentage of positive sewage samples
THE LANCET • Vol 353 • June 12, 1999
2039
Disease severity Moderate/severe
Mild
PaO2* Number of patients
<9·3 15
>9·3 11
Genotypes
B2a1, B 2d1, A 4a3 B1a3 B1a3 B1 a3, B1c1 B1a3, Ca3 B1b1
B2 a1 B2a1 B2 a1, B2a2 B2a1, B 1d1 B2a1 B2a1 , B1a1, B 1a3, B1e1 , B1e2, B1e3, B2 a2, B2a3, B2a3, B3 a3 B2a3, B 1a2, B2 a3, B1a3, B4a3, B1 a1 B1a3 B1b1 B1b2 B1f
B1b1 B1b1, B1 b2 B1d1† B2a5 A2c1 A2c1 A2c1 A4a3 Ca3 † Clinical variables Duration of symptoms (weeks) Use of primary prophylaxis CD4 lymphocyte count (cells/L) Pulmonary co-pathology
1–8 (2) 4 10–310 (60) 1
1–3 (2) 6 10–100 (65) 3
Data are range (median). Key: *kPa, breathing room air. †Patient died.
P carinii ITS sequence types and clinical variables in first episode PCP
more than one type was found, indicative of a mixed infection. The 26 patients with a first episode of PCP were divided into two groups based on their arterial oxygen tension on admission and the need for adjuvant glucocorticoids (table). The two groups were similar in their clinical presentation, CD4 lymphocyte count, use of primary prophylaxis, and presence of pulmonary co-pathogens. ITS type B2a1 was the most frequently identified, in eight patients of whom seven had mild disease, B1a3 was found in seven patients (4 with moderate/severe disease) and type A2c1 was found only in moderate/severe disease. Of 17 episodes of second or third episodes of PCP, four were moderate/severe and 13 were mild. Analysis was confounded by prior administration of anti-P carinii treatment and prophylaxis. However there was still an association of ITS sequence type B2a1 with mild disease, 19/24 (mild) compared with 4/19 (moderate/severe). Type B1a3 was found only in first and not in subsequent episodes of PCP. In contrast, ITS sequence type B2a1, the most common type in this study (and also in other studies4) was the most frequently identified in samples from second and third episodes, and may represent a more persistent or transmissible genotype of human-derived P carinii. These data suggest that in addition to host factors, the severity of PCP may also be associated wtih ITS sequence type of P carinii. This methodology may be applied to noninvasive samples such as oropharyngeal washes,5 and might be used in clinical practice to provide additional data on which to base treatment decisions, especially use of adjuvant glucocorticoids, and identification of patients requring inpatient-based treatment of PCP. We thank Anthony G Tsolaki for sequence data. 1
National Institutes of Health, University of California Expert Panel for Corticosteroids as Adjunctive Threapy for Pneumocystis Pneumonia Consensus statement on the use of corticosteroids as adjunctive therapy for Pneumocystis pneumonia in the acquired immunodeficiency syndrome. N Engl J Med 1990; 323: 1500–04. 2 Lu J-J, Bartlett MS, Shaw MM, et al. Typing of Pneumocystis carinii strains that infect humans based on nucleotide sequence variations of intenal transcribed spacers of rRNA genes. J Clin Microbiol 1994; 32: 2904–12. 3 Tsolaki AG, Miller RF, Underwood AP, Banerji S, Wakefield AE. Genetic diversity at the internal transcribed spacer regions of the rRNA operon among isolates of Pneumocystis carinii from AIDS
2040
patients with recurrent pneumonia. J Infect Dis 1996; 174: 141–56. 4 Lee C-H, Helweg-Larsen J, Tang X, et al. Update on Pneumocystis carinii f. sp. hominis typing based on nucleotide sequence variations in internal transcribed spacer regions of rRNA genes. J Clin Microbiol 1998; 36: 734–41. 5 Tsolaki AG, Miller RF, Wakefield AE. Oropharyngeal samples for genotyping and monitoring of response to treatment of Pneumocystis carinii in persons with AIDS. J Med Microbiol (in press). Department of Sexually Transmitted Diseases, Windeyer Institute of Medical Sciences, Royal Free and University College Medical School, London WC1E 6AU, UK (R F Miller e-mail: [email protected]) and Molecular Infectious Diseases Group, Department of Paediatrics, Institute of Molecular Medicine, Oxford
Intake of trans fatty acids and prevalence of childhood asthma and allergies in Europe Stephan K Weiland, Erika von Mutius, Anika Hüsing, M Innes Asher, on behalf of the ISAAC Steering Committee
Intake of certain polyunsaturated fatty acids, particularly n3 and n-6 fatty acids, has been associated with the development of asthma and allergies in children, but little is known whether the configuration (cis or trans) of these fatty acids plays a role. We investigated the association between intake of trans fatty acids and the prevalence of childhood asthma and allergies in ten European countries. Detailed data on the intake of trans fatty acids and other fatty acids in 14 European countries have recently been provided by a collaborative study that used representative market baskets per country.1 Trans fatty acids occur in dairy products, fat of ruminant animals, and industrially hydrogenated vegetable fats (such as margarine). The International Study of Asthma and Allergies in Childhood (ISAAC) has studied the prevalence of asthma, allergic rhinoconjunctivitis, and atopic eczema in children aged 13–14 years in 155 centres around the world using standardised written and video questionnaires.2 Prevalence estimates were available for 55 study centres in ten countries with data on fatty acid intake: Belgium (1 study centre), Finland (4), France (5), Germany (2), Greece (1), Italy (13), Portugal (4), Spain (8), Sweden (2), UK (15). Linear regression analysis was used to assess the association between the 12-month prevalence of symptoms of asthma (wheeze), allergic rhinoconjunctivitis (runny nose with itchy eyes), and atopic eczema (flexural dermatitis) in those aged 13–14 years and the intake of fatty acids using the country estimate for all centres in the respective countries. There was a positive association between the intake of trans fatty acids (expressed as percent of energy intake) and the prevalence of symptoms of asthma, allergic rhinoconjunctivitis, and atopic eczema (figure). After adjustment for gross national product of the country all these associations remained statistically significant (p<0·001), as was the association with the prevalence of asthma symptoms during the last year assessed by the video questionnaire (p<0·05, data not shown). The associations tended to be stronger when the analyses were restricted to estimates of trans fatty acid intake from sources that contain predominantly hydrogenated vegetable fat, such as oils, biscuits, cakes, and chips.1 Similarly consistent associations were not seen for intake of monounsaturated or polyunsaturated fatty acids in cis configuration. Ecological studies allow comparison of populations with large differences in exposures, but an observed association between populations does not necessarily exist also between individuals. The estimates of trans fatty acid intake
THE LANCET • Vol 353 • June 12, 1999