Time to detection of the growth of Mycobacterium tuberculosis in MGIT 960 for determining the early bactericidal activity of antituberculosis agents.

Evaluation of early bactericidal activity (EBA) by the determination of a fall in viable colony-forming units (CFU) of Mycobacterium tuberculosis in sputum is a first step in the clinical study of new antituberculosis agents. The time to detection (TTD) of growth in liquid media is more sensitive and could substitute for CFU counting on solid media. Overnight sputum samples collected during the evaluation of the novel agent TMC207 in comparison to isoniazid and rifampicin were studied. For the determination of CFU, we incubated 10-fold dilutions of homogenized sputum on selective 7H10 agar. The TTD was measured by incubating decontaminated sputum in the BACTEC MGIT 960 system. The fall in bacillary load over 7 days determined by CFU counting closely matched the prolongation of the TTD in the BACTEC MGIT 960 system. The CFU counts correlated significantly with the TTD. While the ranking of agents and different dosages of TMC207 was similar, the highest dose of TMC207 showed markedly better activity when measured by the TTD than CFU counting when compared to the activity of isoniazid. Automated TTD could augment, or, in future, replace, CFU counting to determine sputum bacillary load in EBA clinical trials pending a more formal evaluation of the correlation of the measurements.

Pyridoxal-5-phosphate plasma concentrations in children receiving tuberculosis chemotherapy including isoniazid.

AIM: Little is known about pyridoxine nutriture of children treated with isoniazid (INH) regimens. This study documents plasma pyridoxal 5'-phosphate (PLP) concentrations in children, HIV-infected and HIV-uninfected, receiving INH regimens. METHODS: Children from the Western Cape of South Africa hospitalized for tuberculosis (TB) management were studied. Plasma PLP concentrations were determined on enrolment, 1-month after commencing TB treatment, and again after 4-month's treatment. The children received a supplement meeting pyridoxine requirements. RESULTS: Nineteen HIV-infected and 33 HIV-uninfected children received INH (dosage range 4-20 mg/kg) daily. Mean PLP plasma concentrations on enrolment were 8.32 (SD 6.75) ng/mL and 11.28 (SD 3.02) ng/mL in HIV-infected and HIV-uninfected children, respectively (p = 0.11) and after 4-month's treatment 6.75 (SD 2.71) ng/mL and 14.76 (SD 7.96) ng/mL (p < 0.001). On enrolment 9 (50%) HIV-infected and 5 (15%) HIV-uninfected children (p = 0.016) had suboptimal PLP concentrations (<6 ng/mL); after 4-month's treatment 8 (42%) and 2 (6%) (p = 0.004). CONCLUSION: Plasma PLP concentrations in children treated for TB were low on enrolment in HIV-infected and HIV-uninfected children; after 4-month's treatment low values were still common in HIV-infected children. Additional pyridoxine supplementation of malnourished children treated for tuberculosis is advisable, particularly those HIV-infected.

Ethambutol dosage for the treatment of children: literature review and recommendations.

The currently recommended daily dose of ethambutol (EMB) for the treatment of tuberculosis (TB) in children varies from a maximum daily dose of 15 mg/kg body weight daily (without a range) to 15-20 mg/kg and 20 mg/ kg (range 15-25 mg/kg). Published evidence relating to the dosage, toxicity and pharmacokinetics of EMB in children and adults is reviewed and a dose of EMB for use in childhood is recommended. Using key words 'ethambutol', 'childhood', 'TB', 'pharmacokinetics', 'bioavailability' and 'toxicity', Medline searches were conducted; cross-references were sought from original papers, books and conference proceedings dating from 1961. When English summaries were available, data were extracted from papers in languages other than English. EMB has a dose-related efficacy best seen when given to adults alone or with a single other drug. Together with isoniazid (INH), a dose of 15 mg/kg EMB gave better results than 6 mg/kg, and 25 mg/kg better than 15 mg/kg. The occurrence of ocular toxicity was also dose-related; >40% of adults developed toxicity at doses of >50 mg/ kg, and 0-3% at a dose of 15 mg/kg/daily. Peak serum EMB concentrations increase in relation to dose, but are significantly lower in children receiving the same dosage. In only 2 of 3811 children (0.05%) receiving EMB doses of 15-30 mg/kg was EMB stopped due to possible ocular toxicity; children of all ages can be given EMB in daily doses of 20 mg/kg (range 15-25 mg/kg) and three times weekly intermittent doses of 30 mg/kg body weight without undue concern.

Monitoring the ingestion of anti-tuberculosis drugs by simple non-invasive methods.

This investigation retrospectively assessed inexpensive non-invasive qualitative methods to monitor the ingestion of anti-tuberculosis drugs isoniazid, rifampicin and rifapentine. Results showed that commercial test strips detected the isoniazid metabolites isonicotinic acid and isonicotinylglycine as efficiently as the isonicotinic acid method in 150 urine samples. The presence of rifamycins in urine samples (n=1085) was detected by microbiological assay techniques and the sensitivity compared to the n-butanol extraction colour test in 91 of these specimens. The proportions detected by the two methods were significantly different and the sensitivity of the n-butanol procedure was only 63.8% (95% CL 51.2-76.4%) as compared to that of the superior microbiological method. Final validation (n=691) showed that qualitative assays measure isoniazid and rifamycin ingestion with an efficiency similar to high-performance liquid chromatography. The qualitative procedures may therefore be valuable in clinical trials and in tuberculosis clinics to confirm drug ingestion.

The influence of human N-acetyltransferase genotype on the early bactericidal activity of isoniazid.

The elimination of isoniazid is subject to the influence of the N-acetyltransferase 2 (NAT2) genotype, and individuals may be homozygotic slow, heterozygotic fast, or homozygotic fast acetylators of isoniazid. The early bactericidal activity (EBA) of an antituberculosis agent can be determined by quantitative culture of Mycobacterium tuberculosis in sputum samples obtained from patients with pulmonary tuberculosis during the first days of treatment. In these studies, the EBA of isoniazid during the first 2 days of treatment was determined for 97 patients with sputum smear-positive pulmonary tuberculosis following isoniazid doses of < or =37.5 mg, 75 mg, 150 mg, 300 mg, and 600 mg. The NAT2 genotype was determined in 70 patients, and the association between EBA and genotype was examined in this subgroup. Similarly, the relationship between EBA and isoniazid serum concentration was evaluated in 87 patients. The mean EBA of isoniazid increased with dose, but it levelled off between doses of 150 mg (mean EBA, 0.572) and 300 mg (mean EBA, 0.553). Significant differences were found in the mean EBA of isoniazid between the homozygous slow acetylator group and the heterozygous fast acetylator group and between the homozygous slow acetylator group and the homozygous fast acetylator group, but not between the heterozygous fast acetylator group and the homozygous fast acetylator group. The EBA appeared to reach a maximum at a 2-h isoniazid concentration of 2-3 microg/mL. These data confirm a significant effect of NAT2 genotype on the EBA of isoniazid over a range of doses.

The factor structure for positive and negative symptoms in South African Xhosa patients with schizophrenia.

Most studies investigating the symptom dimensions of schizophrenia utilising the Scale for the Assessment of Negative Symptoms (SANS) and the Scale for the Assessment of Positive Symptoms (SAPS) favour a three factor model. This study sought to investigate the factor structure of both the global and individual items of the SANS and SAPS in a large sample of South African Xhosa patients with schizophrenia. A total of 422 subjects participated. Both principal components and factor analytical procedures were applied. For the global items, a two-factor solution representing positive and negative symptoms accounted for 59.9% of the variance. Alternatively, the three-dimensional model of negative, psychotic and disorganisation factors was supported by a five-factor solution if the more heterogeneous items of attention and alogia were ignored. Analysis of the individual items yielded a five-factor solution with the negative symptoms splitting into diminished expression and disordered relating, and the positive symptoms separating into factors for psychosis, thought disorder and bizarre behaviour. Our findings are very similar to those from other parts of the world, providing evidence that the factor structure for the symptoms of schizophrenia is relatively resistant to cultural influences. This is particularly true for negative symptoms.

Early bactericidal activity of antituberculosis agents.

The early bactericidal activity (EBA) of an antituberculosis agent is arbitrarily defined as the fall in log(10) colony forming units (cfu) of Mycobacterium tuberculosis per ml sputum per day during the first 2 days of treatment. Determining the EBA is an important preliminary step in the clinical evaluation of an antituberculosis agent. We review the results of eight published studies of the EBA of different antituberculosis agents, the impact of these results on our understanding of the actions of the respective agents, the clinical characteristics and sputum findings of patients included in these studies, and explore sources of variation in the EBA results. Patients in these studies had a mean age of 31-36 years, a mean weight of 50-57 kg, 67% were male and 56% had lung involvement covering an area of more than one lung, and 90% had multicavitary disease. None of these findings were related to EBA in any study. The mean log(10) cfu per ml sputum in the first specimen was 6.474. This was related to radiological extent of disease and cavity size in one study (p < 0.001) and, in the case of isoniazid to EBA with a rise in EBA of 0.094 (95% CL 0.029-0.158) for each tenfold rise in cfu counts/ml sputum. The overall variation in EBA in these studies was 0.0303, that due to laboratory processing of specimens was 0.0011, and due to patient characteristics and sputum sampling 0.0212. The EBA is a reproducible investigation that has contributed significantly to our knowledge of the actions and characteristics of both established and new antituberculosis agents. The greatest source of variation in EBA results appears to be that due to interpatient variation in disease characteristics and sputum sampling.

Lecithin:cholesterol acyltransferase activity and high-density lipoprotein subfraction composition in type 1 diabetic patients with improving metabolic control.

On initial diagnosis or when metabolic control is poor, subjects with type 1 (insulin-dependent) diabetes mellitus often exhibit decreased high density lipoprotein (HDL) cholesterol levels, which have been associated in numerous studies in non-diabetic subjects with atherosclerosis and coronary artery disease. We measured the activities of plasma lecithin:cholesterol acyltransferase (LCAT), post-heparin lipoprotein lipase, and the composition of the HDL subfractions HDL2 and HDL3, in ten poorly controlled type 1 diabetic patients admitted to a metabolic ward (six women and four men, aged 18-37 years). The measurements were repeated after metabolic control had been optimised and again a week after discharge. The results were compared with those of ten healthy normolipidaemic subjects matched for age, sex and body mass. LCAT activity increased significantly (P < 0.05) with improved metabolic control in the diabetic patients, and showed positive within-person correlation with HDL2 cholesterol ester (r = 0.67; P < 0.01), HDL2 free cholesterol (r = 0.67; P < 0.01), phosphatidylcholine (r = 0.49; P < 0.05), total phospholipids (r = 0.50; P < 0.01) and apolipoprotein A-I (apo A-I: r = 0.72; P < 0.01). With improving metabolic control HDL2 lipid levels increased more than twofold and the compositional changes in HDL2 were reflected by an increased apo A-I:apo A-II ratio (P < 0.05) and a decreased triglyceride:apo A-I ratio (P < 0.05). Changes in HDL3 levels and composition were minor. The results of this study indicate that an increase in LCAT activity increases the concentration and changes the composition of HDL2 in type 1 diabetic patients with improved metabolic control.

Primipaternity and duration of exposure to sperm antigens as risk factors for pre-eclampsia.

OBJECTIVE: To establish whether primipaternity and duration of unprotected sexual cohabitation is associated with an increased risk of pre-eclampsia. METHOD: At a tertiary referral center, the study had a case and control group of 60 multigravid women each, as well as a case and control group of 50 primigravid women each. Information was compiled by means of a confidential questionnaire. RESULT: After multiple logistic regression analysis using age, smoking, hypertension in previous pregnancies, change of paternity and duration of unprotected sexual cohabitation as predictors, the regression coefficients for change of paternity and sexual cohabitation of longer than 6 months in multigravid women were -0.4 (P = 0.15) and -1.4 (P = 0.03), respectively. CONCLUSION: Multigravid women with a period of unprotected sexual cohabitation of longer than 6 months had a decreased risk of pre-eclampsia. Primipaternity was not a significant risk factor for pre-eclampsia.

Facial profile changes with various orthodontic premolar extraction sequences during growth.

The Visual Treatment Objective (VTO) is an extremely valuable tool in the process of working out the treatment plan for the individual. This is especially true for the inexperienced operator. Often it becomes clear that extractions are indicated, but there remains uncertainty as to which teeth should be chosen for extractions to give the best results. As it is necessary to express the expected change in profile due to growth of the nose and also of the chin, VTO construction is helpful in determining the extraction decision. Clinical experience and research projects have indicated that the use of mean values has definite limitations when constructing a VTO for an individual. The primary objective of this investigation was to provide formulae by means of which anteroposterior changes in the facial profile of growing individuals for whom four premolar extraction treatment is proposed can be predicted with a greater measure of certainty. The records of 248 growing Caucasian orthodontic patients (120 males and 128 females) were selected and divided into Group 44 (four first premolar extractions), Group 45 (upper first premolar and lower second premolar extractions) and Group 55 (four second premolar extractions). Formulae are presented for the prediction of the amount of incisor retraction, anteroposterior nose growth and for chin growth. The formulae were derived by regression of incisor retraction, anteroposterior nose growth and chin growth on various predictors, and could be used in the construction of VTO's for selected cases.

Pyrazinamide pharmacokinetics and efficacy in adults and children.

Pyrazinamide (PZA) is an essential sterilizing drug and with rifampicin enables six-month short-course antituberculosis chemotherapy. Despite routine use for nearly forty years uncertainty remains regarding the most appropriate PZA dosage for children. In view of this uncertainty literature relating to the efficacy and pharmacokinetics of PZA in children treated for tuberculosis and in adult volunteers and patients was reviewed. Making use of the PZA maximum concentration (C(max)) following various PZA dosages in different groups straight line regression of concentration on dosage was fitted through the origin by least squares and weighted for the numbers of subjects. The fitted line offers an approximation of the likely PZA C(max) that would result from a particular dosage. The slopes of C(max)/dosage of the fitted lines are 1.32 (SE 0.099) for paediatric patients, 1.36 (SE 0.051) for adult volunteers and 1.35 (SE 0.037) for adult patients; there is little difference between the C(max) concentrations achieved in children and adults, whether patients or healthy volunteers, following various mg/kg body weight dosages, suggesting that children and adults receiving the same mg/kg body weight PZA dosage will reach a similar C(max). Children can receive the same mg/kg body weight PZA dosage as adults.

Time to liquid culture positivity can substitute for colony counting on agar plates in early bactericidal activity studies of antituberculosis agents.

The measurement of early bactericidal activity (EBA) is the first step in the clinical investigation of antituberculosis agents. EBA is determined by quantifying the viable sputum mycobacterial load on consecutive days of treatment. To investigate whether time to positivity (TTP) in mycobacterial liquid culture can substitute for colony forming unit (CFU) counting on agar plates we compared the error variation of TTP and CFU in 2115 pooled sputum samples collected overnight from 250 individuals included in five EBA studies. We found that the technical variation between duplicate laboratory measurements and the within-subject or day-to-day variation were similar for TTP (8.5% and 27.4% of total variation, respectively) and CFU (6.7% and 29.3% of total variation). The ability of the measurements to separate the EBA of 22 treatment arms was determined with group rank correlation of means and one-way analysis of variance. Except for the EBA over 0-2 days, individual and group EBAs measured with TTP and CFU were highly correlated. Treatment group means rank correlation coefficients were r=0.472, r=0.910 and r=0.818, respectively, for EBA 0-2 days, EBA 0-7 days and EBA 0-14 days. Analysis of variance significantly favoured TTP over CFU for discrimination between groups with F values of 6.58 and 1.87, 7.77 and 4.58, and 8.71 and 3.56, respectively. We conclude that TTP is an acceptable alternative to CFU counting for the determination of the viable sputum mycobacterial load in EBA studies of up to 14 days duration.

The pharmacokinetics and pharmacodynamics of rifampicin in adults and children in relation to the dosage recommended for children.

The dosages of antituberculosis agents recommended for treatment of childhood tuberculosis often reflect those for adult patients with similar mg/kg body weight dosages and ranges advised. Literature relating to the pharmacokinetics and pharmacodynamics of rifampicin (RMP) is reviewed and the serum concentrations reached by adults, both patients and healthy volunteers and children, established or not established on RMP, compared. Straight line regression of maximum RMP serum concentrations (C(max)) on dosage, weighted for the number of individuals, found slopes (SE) of 1.025 (0.067) and 0.881 (0.046) respectively for adult volunteers not established and established on RMP (P = 0.076), and similarly 0.748 (0.057) and 0.684 (0.038) respectively for adult patients (P < 0.001) and 0.622 (0.050) and 0.368 (0.041) respectively for children (P < 0.001). These results indicate that for equivalent RMP dosages adult patients reach a lower C(max) than adult volunteers and that adults, both volunteers and patients established on RMP reach higher C(max) values than children; children established on RMP require approximately twice the mg/kg body weight dosage of RMP to reach serum concentrations equivalent to those of adults. It is noteworthy that many adult patients receiving currently recommended RMP dosages also do not reach the often recommended RMP 2 h serum concentration of 8 µg/mL.

Early bactericidal activity of high-dose rifampin in patients with pulmonary tuberculosis evidenced by positive sputum smears.

We studied the early bactericidal activity of twice the standard dose of rifampin in subjects with pulmonary tuberculosis evidenced by positive smears. The observed mean 2-day activity was almost double that reported at the standard dose. Further studies are warranted to establish whether higher rifampin doses might assist in shortening tuberculosis treatment.

The influence of dose and N-acetyltransferase-2 (NAT2) genotype and phenotype on the pharmacokinetics and pharmacodynamics of isoniazid.

OBJECTIVE: This study evaluated the pharmacokinetics of isoniazid (INH) associated with optimal early bactericidal activity (EBA), defined as 90% of the maximum EBA (EBA(90)) and the influence of N-acetyltransferase-2 (NAT2) subtype on the ability of pulmonary tuberculosis (PTB) patients to reach the identified pharmacokinetic values after INH doses ranging from 0.2 to 10-12 mg/kg body weight. METHODS: INH serum concentrations and NAT2 subtype were determined during four studies of PTB patients in three of whom the EBA of INH was determined. The relationship of EBA to area under the curve (AUC) (AUC(0-infinity)) and 2-h serum concentrations was examined by exponential regression and fitted curves estimated the AUC(0-infinity) and 2-h serum concentrations at which EBA(90) was reached. RESULTS: EBA(90) was reached at an AUC(0-infinity) of 10.52 microg/ml per hour and 2-h serum concentrations of 2.19 microg/ml. An AUC(0-infinity) of 10.52 microg/ml per hour was reached by all 66 patients receiving a 10-12 mg/kg INH dose and all 21 receiving 6 mg/kg, except 1 of 10 (10%) homozygous fast (FF) acetylators; however, at 5 mg/kg, 4 of 12 (33%) FF and 26 of 27 (96%) heterozygous fast (FS), but all 21 homozygous slow (SS) acetylators did so; and 1 of 3 (33%) FF, 2 of 6 (33%) FS, but all 4 SS acetylators at dose 3 mg/kg. An INH 2-h serum concentration of 2.19 microg/ml was reached by all 66 patients receiving 10-12 mg/kg and all 21 receiving 6 mg/kg, except for 2 (20%) FF acetylators at a dose of 5 mg/kg; however, only 3 (25%) of 12 FF acetylators, but 26 (96%) of 27 FS acetylators, and all 21 SS acetylators reached this concentration; and at a dose of 3 mg/kg, 1 (33%) of 3 FF acetylators, 2 (33%) of 6 FF, but all 4 SS acetylators. CONCLUSIONS: At a 6 mg/kg dose, all except a minority of FF NAT2 acetylators, achieve an INH AUC(0-infinity) and 2-h INH serum concentrations associated with EBA(90), as did all 4 SS acetylators receiving 3 mg/kg. Any dose reduction below 6 mg/kg body weight will tend to disadvantage a significant proportion of faster acetylators, but, conversely, SS acetylators require only a 3 mg/kg dose to achieve a satisfactory exposure to INH.

Isoniazid pharmacokinetics in children treated for respiratory tuberculosis.

AIMS: To define the pharmacokinetics of isoniazid (INH) in children with tuberculosis in relation to the N-acetyltransferase 2 (NAT2) genotype. METHODS: The first order elimination rate constant (k) and area under the concentration curve (AUC) were calculated in 64 children <13 years of age (median 3.8) with respiratory tuberculosis from INH concentrations determined 2-5 hours after a 10 mg/kg INH dose. The NAT2 genotype was determined; 25 children were classified as homozygous slow (SS), 24 as heterozygous fast (FS), and 15 as homozygous fast (FF) acetylators. RESULTS: The mean (SD) k values of the genotypes differed significantly from one another: SS 0.254 (0.046), FS 0.513 (0.074), FF 0.653 (0.117). Within each genotype a median regression of k on age showed a significant decrease in k with age. The mean (SD) INH concentrations (mg/l) two hours after INH administration were SS 8.599 (1.974), FS 5.131 (1.864), and FF 3.938 (1.754). A within genotype regression of 2-hour INH concentrations on age showed a significant increase with age. A within genotype regression of 3-hour, 4-hour, and 5-hour concentrations on age also showed a significant increase with age in each instance. In ethnically similar adults, mean (SD) 2-hour INH concentrations (mg/l) for each genotype were significantly higher than the children's: SS 10.942 (1.740), FS 8.702 (1.841), and FF 6.031 (1.431). CONCLUSIONS: Younger children eliminate INH faster than older children and, as a group, faster than adults, and require a higher mg/kg body weight INH dose to achieve serum concentrations comparable to adults.

Models and the use of signed rank tests.

Rank tests are often used to analyse medical and biological data. The lack of invariance of the paired sample Wilcoxon signed rank test with respect to transformation of observations, and the choice of an appropriate rank test in the case of the two way analysis of variance random effects model, are discussed in the context of two medical examples.

The use of statistics to examine the association between fluoride in drinking water and cancer death rates.

"The basis of statistical tests of significance of association between fluoride level in drinking water and cancer death rates is discussed. Reference is made to two reported studies in each of which cancer death rates of a number of [U.S.] cities were used. It is argued that between city variation should be taken into account when performing tests of significance. In one of the two studies this was done informally; in the other between city variation was ignored."

Effects of hypothyroidism and progesterone on mammary tumours induced by 7,12-dimethylbenz(a)anthracene in Sprague-Dawley rats.

Hypothyroidism, alone or combined with progesterone, significantly decreased 7,12-dimethylbenz(a)anthracene (DMBA) mammary tumorigenesis relative to controls. However, the decrease was less in the progesterone-treated group, and statistical analysis showed that progesterone enhanced tumorigenesis to the same extent in hypothyroid animals as in the controls. Most tumours in hypothyroid progesterone-treated rats were adenocarcinomata; in the absence of the hormone most tumours were benign. However, the difference between the tumour types in the 2 groups was not statistically significant.The morphological changes observed in the endocrine glands, genital tracts and non-neoplastic mammary tissue, considered in relation to previously reported data, suggest that hypothyroidism reduced the tumour yield mainly by secondarily inhibiting somatotrophin production and secretion, although the effect of decreased food intake could not be excluded completely. The higher tumour yield in the hypothyroid progesterone-treated rats may have been due to higher circulating levels of prolactin in this group compared with those in the hypothyroid group which received no hormone.