Analysing sequential events in clinical trials

BACKGROUND

Data from clinical trials where the endpoint is a single survival time are readily analysed by standard methods, most commonly using a semi-parametric proportional hazards approach. However, when the outcome involves two sequential survival times, standard methods may not be applicable.

METHODS

We consider methods appropriate for the analysis of survival data in clinical trials where there are two distinct, sequential and opposing survival endpoints and where inferences about the second event are of particular interest. Two motivating examples of randomized clinical trials with different designs provide important illustrations of the methodology in practice.

RESULTS

Bivariate log-normal survival models are proposed as useful way of modeling such data. These models can be simply implemented in two stages, each of which is a univariate log-normal survival analysis. Different approaches to the analyses are described according to whether a second randomized treatment assignment is made at the time when the first event occurs and the second phase of the study commences. In the absence of a second randomization, the bivariate log-normal model adjusts for selection into the second phase of the study.

CONCLUSIONS

The investigation of 'treatment sequences' should, wherever possible, be handled by repeat randomization, which can then be followed by valid, unbiased analyses. However, in many clinical trial scenarios, this is simply not possible. In this case, the best approach is to consider the data as arising from an observational study, whilst controlling for all appropriate covariates.

LIMITATIONS

The approach we describe is appropriate for log-normally distributed data but could be generalised to handle other distributions, although the process of model fitting would be less straight-forward.

Post-exposure HIV prophylaxis following sexual exposure: a retrospective audit against recent draft BASHH guidance

OBJECTIVES

To retrospectively audit the management of post-exposure HIV prophylaxis following sexual exposure (PEPSE) against the British Association for Sexual Health and HIV 2004 draft guidance.

METHODS

A retrospective review of case notes from January 2000 to November 2004. The draft guidelines were not adopted into clinical practice during the study period.

RESULTS

76 patients received PEPSE. 79% (95% CI 68.08 to 87.46) of PEPSE prescriptions were given for exposures that were in accordance with the guidelines' recommended indications (target 90%). 87% (95% CI 77.13 to 93.51) of PEPSE was prescribed within 72 hours of risk exposure (target 90%). 91% (95% CI 81.94 to 96.22) of recipients received a recommended antiretroviral combination. 53% (95% CI 40.84 to 64.21) of recipients completed the PEPSE course (target 75%). 45% of patients attended for the 3 month follow up HIV test but only 12% (95% CI 5.56 to 21.29) attended for both the 3 month and 6 month HIV test (target 75%).

CONCLUSION

PEPSE is predominantly being prescribed for recommended indications and is dispensed within 72 hours of risk exposure. PEPSE completion rates and attendance for 3 months and 6 months post-exposure HIV testing need improving, perhaps by introducing a PEPSE clinic.

What happens to women who sell sex? Report of a unique occupational cohort

BACKGROUND/OBJECTIVES

Sex work has been seen as both a health and a social problem. However, there is a paucity of evidence on the longer term impact on health. We explored the health and career paths over a period of 15 years among women who have worked in the sex industry.

DESIGN

A longitudinal study of sex workers recruited between 1986 and 1993 and followed for 15 years. Outcome data were obtained through interview, clinic records, or third parties.

SETTING

Clinic and community settings in London.

PARTICIPANTS

We obtained outcome data on 130 (37%) of the original cohort of 354 women, with a combined follow up of 1247 years.

MAIN OUTCOME MEASURES

Vital status, most recent occupation, duration of sex work, sexually transmitted infections (STI), major health problems.

RESULTS

The majority (73/124, 59%) were still in the sex industry and had sold sex for a mean of 13.6 years. There were six deaths, a mortality of 4.8 per 1000 person years. Surviving women had a high cumulative risk (110 of 118, 93%) of STI. Past gonorrhoea was associated with pelvic inflammatory disease (RR 2.28, 95% CI 1.12 to 4.66) and infertility (RR 10.9, 95% CI 1.5 to 77.3). Other outcomes included mental health problems (38 of 97, 40%) and addiction (46 of 72, 64%). There were no significant differences in health outcomes between women who were still in the sex industry and those who had stopped. There was a high level of occupational mobility, and 31 women (of 84, 37%) had completed vocational or higher education, including eight to postgraduate level.

CONCLUSIONS

Sex work is associated with excess mortality and morbidity including the sequelae of STI, mental health problems, and substance misuse. The relation between these health problems and sex work is complex.

A phase II study of lapatinib (GW572016) in recurrent/metastatic (R/M) squamous cell carcinoma of the head and neck (SCCHN)

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Background: Epidermal growth factor receptor (EGFR) inhibitors have demonstrated reproducible activity in patients with R/M SCCHN. HER2 is the preferred dimerization partner for EGFR. Lapatinib is a dual EGFR and HER2 kinase inhibitor that has demonstrated promising preclinical activity in SCCHN models. Methods: This phase II multi-institutional study enrolls patients with R/M SCCHN into 2 cohorts: those without prior exposure to an EGFR inhibitor (arm A) and those with prior exposure to an EGFR inhibitor (arm B). All subjects were treated with lapatinib 1500mg OD. Primary endpoints were response rate (arm A) and progression-free survival (arm B). Results: 42 subjects have been enrolled (27 arm A, 15 arm B; 35 male, 7 female, median age 60 years). Toxicity was generally mild without any dose reductions or patient withdrawal due to adverse effects. Diarrhea was the most frequent toxicity occurring in 40% of patients. Other toxicities observed included fatigue (21%), rash (21%) and nausea (14%). 2 patients experienced grade 3 toxicity (1 diarrhea, 1 emesis). 1 patient had a reduction in left ventricular ejection fraction (60% to 40%) which was asymptomatic and recovered to baseline upon discontinuation of lapatinib. No objective responses were observed in either arm. In an intent-to-treat analysis stable disease was the best response observed in 37% of arm A and 20% of arm B subjects. Median PFS was 1.6 months in arm A and 1.7 months in arm B. Conclusions: Lapatinib as a single agent in R/M SCCHN, although well tolerated, appears to have little activity in either EGFR inhibitor naïve or refractory subjects.

No significant financial relationships to disclose.

How safe is safer sex? High levels of HSV-1 and HSV-2 in female sex workers in London

Female sex workers in Europe have low levels of sexually transmitted infections, attributable to condom use. The aim of this paper is to describe the seroepidemiology of HSV-1 and HSV-2 in female sex workers in London by using a 15-year prospective study of 453 sex workers. The seroprevalence of HSV-1 was 74.4% and independently associated with birth in a 'transitional country' (OR 5.4, 95% CI 1.61-18.20). The seroprevalence of HSV-2 was 60% and declined over time; it was also independently associated with time in sex work (OR 2.12, 95% CI 1.23-3.65) and birth in a 'developing country' (OR 2.95, 95% CI 1.34-6.48). We show that a cohort of sex workers with extensive condom use and little known sexually transmitted infection have high levels of HSV-1 and HSV-2 infection, suggesting that condoms may not be universally protective. Sex workers are candidates for HSV vaccine efficacy or intervention studies.

Identification of a novel HLA-A allele (A*1115) in the UK National External Quality Assessment Schemes for Histocompatibility and Immunogenetics' Educational Cell Exchange

The novel allele, HLA-A*1115, was identified in an 'Educational Scheme' sample (ED03/03 - from a north-western European Caucasoid blood donor) distributed by the UK National External Quality Assessment Schemes for Histocompatibility and Immunogenetics. ED03/03 was typed by serology, the polymerase chain reaction using sequence-specific primers and sequence-based typing. A*1115 is most similar to A*110101 with a single mismatch (G to C) at constant position 565, leading to a conservative amino acid change from valine (GTG) to leucine (CTG) at codon 165 in the alpha(2) domain. This substitution has not been reported for any other HLA class I allele so far. The HLA-A*1115-bearing haplotype was B*350101; Cw*040101; DRB1*140101; DRB3*020201; DQA1*010401; DQB1*0503; DPA1*0103/07; DPB1*030101. Extensive serological typing indicated that this allele essentially encodes a 'normal' HLA-A11 specificity.

HLA-DQB1 sequencing-based typing using newly identified conserved nucleotide sequences in introns 1 and 2

Sequencing-based typing (SBT) human leukocyte antigen (HLA) class I and II genes should examine entire exon sequences where polymorphisms lie. Primers for the amplification of complete exons therefore anneal in introns and their design relies on accurate intron sequences being available. We decided to develop a SBT method for HLA-DQB1 using amplification primers which anneal in introns 1 and 2, yet the amount of intron sequence data previously available in databases was sparse. Therefore, we undertook a systematic sequencing of introns 1 and 2 using DNA from cell lines homozygous for DQB1. This study confirmed an earlier report that the non-coding regions of this gene are the most polymorphic seen in the human genome. Intron sequences within an allele group were largely identical, the exceptions being DQB1*0301 differing from other DQB1*03 allele groups and DQB1*0601 differing from all other DQB1*06 alleles. A retroviral Alu element, related to the AluYa5a2 subfamily, was identified uniquely inserted in intron 2 of DQB1*02 alleles. For the typing approach, six amplification primers were designed based on conserved allele group sequences covering all of the HLA DQB antigens, and two sequencing primers were also designed which anneal in intron 2. This method has proved to be very robust and has been used as part of a referral DNA sequencing service for a number of years.

A new HLA-A Allele, HLA-A*6824, identified in three unrelated individuals*

A novel allele, human leukocyte antigen (HLA)-A*6824, has been identified in three unrelated individuals of northwestern European origin in a period of less than 4 months, implying that this allele may be quite common in this population. HLA-A*6824 differs from A*680102 by a single nucleotide change at position 275 in exon 2, which results in a conservative amino acid substitution from lysine to arginine in the peptide-binding groove at codon 68.

Synchronous tumors: Hodgkin disease presenting in mesenteric lymph nodes from a right hemicolectomy for colon carcinoma

The authors report the case of a 56-year-old male diagnosed with Hodgkin disease involving the mesenteric lymph nodes recovered from a right hemicolectomy for colonic adenocarcinoma. The liver and bone marrow were also involved by Hodgkin disease. Synchronous colonic carcinoma and lymphoma in the same patient is a rare occurrence, and Hodgkin disease involving the mesenteric lymph nodes is uncommon as well.

Declining prevalence of STI in the London sex industry, 1985 to 2002

OBJECTIVES

To describe major changes in the London sex industry between 1985 and 2002 and assess the implications for sexually transmitted infection (STI) risk.

METHOD

A descriptive study comparing women who first attended a sex work clinic between 1996 and 2002 and those first attending from 1985 to 1992; a nested case-control study. 1050 female sex workers took part. The setting was a specialist clinical service for sex workers based in a London genitourinary medicine (GUM) clinic, and fieldwork in west London. The main outcome measures were reported condom use and prevalent STI.

RESULTS

Over the period of the study there was a significant increase in the proportion of sex workers not born in the United Kingdom (from 25% to 63%, p < 0.001), and women entered sex work at an older age (median 24 years compared with 20 years, p < 0.001). Condom use increased (with the exception of oral sex). There was a significant decline in the proportion of participants reporting a previous STI (32% compared with 80%, p < 0.001) and the prevalence of acute STI declined from 25% to 8% (p < 0.001). Acute STI was associated with younger age, younger age at first sex work, being new to sex work, and inconsistent condom use. In a multivariate analysis unprotected sex with clients was the only significant risk.

CONCLUSION

Major restructuring of the sex industry, including the shift to a primarily migrant workforce, has been associated with a steep decline in acute STI, undermining popular assumptions that migrant sex workers are central to the ongoing STI epidemic. We attribute the decline in acute STI to an increase in safer sex.

Improving uptake of HIV testing in patients with a confirmed STI

Up to 70% of GU clinic attendees with a sexually transmitted infection (STI) and undiagnosed HIV, remain HIV undiagnosed after their visit. STIs have been shown to facilitate HIV transmission. Therefore, patients with an STI should test for HIV. Our objective was to compare the uptake of HIV testing in GU clinic attendees with an STI (study group) with those receiving a negative GU screen (control group). This re-audit was performed after introduction of the following clinic changes: nurse-performed asymptomatic GU screening; 'opt-out' HIV testing policy; discontinuing routine pre-HIV test counselling; access to HIV results by post. The uptake of HIV testing overall, and in the study and control groups respectively was 53% (n = 573), 41% (n = 285) and 65%, showing significant improvement compared to the first audit in 1999 (18%, 14% and 33% respectively) (P < 0.01). The clinic interventions increased HIV testing rates which were in keeping with National Sexual Health strategy targets.

Establishment of Serratia entomophila after application of a new formulation for grass grub control

The bacterium Serratia entomophila is a naturally occurring pathogen causing amber disease of the New Zealand grass grub (Costelytra zealandica) A novel granular formulation of S entomophila Bioshieldtrade; was applied to 18 pasture sites in a largescale programme to demonstrate efficacy against grass grub No significant difficulties were encountered in application of the granules through conventional machinery There were high populations of the applied bacteria in soil within the first week of application and within 6 weeks of application there was an average of 3 x 104 viable S entomophila of the applied strain per gram of soil This resulted in a significant (Plt;005) 20 increase in the incidence of amber disease in the treated grass grub populations compared to untreated populations Successful establishment of the bacteria in the soil and target population following Bioshieldtrade; granule application was demonstrated on a wide range of sites under various farming conditions

Identification of a new allele, HLA-DRB1*1360, on a DRB5 haplotype in a Brazilian individual

The application of DNA-based methods for human leukocyte antigen (HLA) genotyping has revealed an ever-increasing degree of polymorphism within the HLA-DRB loci and has resulted in the discovery of new alleles. We have identified a new DRB1 allele that was subsequently named DRB1*1360 by the WHO Nomenclature Committee. This allele is unusual for a DRB1*13 allele, as it is present on a DRB5 haplotype rather than the normal DRB3 haplotype found in association with DRB1*13 alleles.

Progressive increase in incidence and prevalence of multiple sclerosis in Newcastle, Australia: a 35-year study

The prevalence of multiple sclerosis (MS) in Newcastle, Australia increased significantly between 1961 and 1981 and the incidence of the disease also increased between the decades 1950-1959 and 1971-1981. The present study sought to determine whether there has been a further increase in the frequency of MS in the subsequent 15 years, and to examine the potential factors underlying this change. The incidence, prevalence and clinical profile of multiple sclerosis were therefore re-examined in Newcastle, Australia in 1996 using comparable diagnostic criteria and methods to those employed in studies in the same region in 1961 and 1981. There has been a significant progressive increase in prevalence from 19.6 to 59.1 per 100,000 population and a significant increase in incidence from 1.2 to 2.4 per 100,000 population from 1961 to 1996. The most pronounced increase in prevalence was in females and in the age-group over 60 years, and there was also an increased incidence in females aged 20-29 years. There was little change in the age of disease onset, but duration of disease in females had increased substantially. The significant increase in prevalence is attributed to increased incidence, particularly in females; and to increased survival. Although such trends in prevalence have been observed in the Northern Hemisphere, this is the first such study in the Southern Hemisphere to show a longitudinal increase in prevalence and incidence over a period of this duration.

A new allele, HLA-DRB4*010304

We report here the identification of a novel DRB4*01 allele, DRB4*010304, found in a patient waiting for a liver transplantation. The new allele was detected during a routine DNA-based HLA typing. Sequencing confirmed that the new allele is identical to DRB4*01030101 at exon 2 except for position 216 where the new allele has a T instead of a C.

Identification of HLA alleles with low or no cell surface expression in the Czech population

The presence of the A*24020102L allele is implicated in one donor from the CBMD who serologically was typed as A2; B44, B55; Cwl, Cw7. The DRB4*01030102N allele was identified in one healthy donor and in one patient with MDS during routine HLA class II DNA typing. The DRB4*01030102N allele was identified in the patient's father, who had CML, and was associated with the HLA-A3-B7-Cw7-DRB1*0701-DQB1*0303 haplotype, which is common for European populations. In order to avoid mistyping, both techniques, serology and molecular biology must be used for HLA typing, especially for cases where just one antigen appeared to be present using serological methods.

Identification of two new alleles in a single Korean individual, HLA-B*1568 and HLA-DRB1*1208

We have identified a new HLA-B*15 allele and a new HLA-DRB1*12 allele, named B*1568 and DRB1*1208, respectively. The alleles were identified using a combination of sequence specific primers, reverse line sequence specific oligonucleotide probing and sequence-based typing. Both alleles were identified in a single individual of Korean origin. HLA-B*1568 appears to be an HLA-B*4801/B*1507 hybrid combining the exon 2 sequence of B*4801 and the exon 3 and 4 sequences of B*1507. Exon 2 of DRB1*1208 was most similar to DRB1*1201 or 1206, with a single mismatch at nucleotide position 165 (A to C). At the protein level, this substitution results in a phenylalanine substitution at position 26 that creates an identical amino acid sequence to DRB3*0202 between amino acid positions 17 and 36.

Identification of a new HLA-B*15 allele, HLA-B*1569

We have identified a new HLA-B*15 allele (B*1569) by polymerase chain reaction (PCR) using sequence-specific primers (SSP) and sequence-based typing (SBT). This novel allele was found in a 67-year-old white Caucasian male and differs from HLA-B*1503 at 3 positions. The nucleotide substitutions at positions 544, 559 and 560 result in amino acid changes at codon 158 from GCC (alanine) to ACC (threonine), and at codon 163 from CTG (leucine) to ACG (threonine).

Attitudes towards intramural continuing medical education: a european perspective

Continuing medical education (CME) is now one of the key areas of development in medical education. This paper describes the development of an intramural continuing medical education programme de novo in a newly opened cancer institute in Italy, which provided a unique opportunity to study attitudes towards the concepts and goals of continuing medical education as most of the individuals involved in this programme were exposed to continuing medical education for the first time. The continuing medical education programme was overseen by a CME committee for 1 year. Three 1-hour sessions were delivered each week and one credit point was awarded for each session. The sessions included grand rounds, clinical-based teaching and a 3-weekly rotating schedule of pathology, radiology and research. Participants were all the medical doctors attending the European Institute of Oncology. Attendance at greater than 50% of the total sessions available yearly qualified the individual for certification by the CME committee of the Institute. A questionnaire was circulated to all medical doctors at the Institute at the end of the academic year to assess attitudes to CME in general. Forty-six out of 84 questionnaires were returned. The majority of those involved in this CME intramural programme undertook self-directed CME activities and at least 50% had not previously attended either grand rounds or research seminars. Most felt that CME should not be mandatory but that its activities should be monitored. The greatest difficulty with CME was in its timing.