Mechanistic mathematical models: An underused platform for HPV research

Health economic modeling has become an invaluable methodology for the design and evaluation of clinical and public health interventions against the human papillomavirus (HPV) and associated diseases. At the same time, relatively little attention has been paid to a different yet complementary class of models, namely that of mechanistic mathematical models. The primary focus of mechanistic mathematical models is to better understand the intricate biologic mechanisms and dynamics of disease. Inspired by a long and successful history of mechanistic modeling in other biomedical fields, we highlight several areas of HPV research where mechanistic models have the potential to advance the field. We argue that by building quantitative bridges between biologic mechanism and population level data, mechanistic mathematical models provide a unique platform to enable collaborations between experimentalists who collect data at different physical scales of the HPV infection process. Through such collaborations, mechanistic mathematical models can accelerate and enhance the investigation of HPV and related diseases

Adding a quadrivalent human papillomavirus vaccine to the UK cervical cancer screening programme: A cost-effectiveness analysis

<p>Abstract</p> <p>Background</p> <p>We assessed the cost-effectiveness of adding a quadrivalent (6/11/16/18) human papillomavirus (HPV) vaccine to the current screening programme in the UK compared to screening alone.</p> <p>Methods</p> <p>A Markov model of the natural history of HPV infection incorporating screening and vaccination was developed. A vaccine that prevents 98% of HPV 6, 11, 16 and 18-associated disease, with a lifetime duration and 85% coverage, in conjunction with current screening was considered.</p> <p>Results</p> <p>Vaccination with screening, compared to screening alone, was associated with an incremental cost-effectiveness ratio of £21,059 per quality adjusted life year (QALY) and £34,687 per life year saved (LYS). More than 400 cases of cervical cancer, 6700 cases of cervical intraepithelial neoplasia and 4750 cases of genital warts could be avoided per 100,000 vaccinated girls. Results were sensitive to assumptions about the need for a booster, the duration of vaccine efficacy and discount rate.</p> <p>Conclusion</p> <p>These analyses suggest that adding a quadrivalent HPV vaccine to current screening in the UK could be a cost-effective method for further reducing the burden of cervical cancer.</p

Impact of coverage-dependent marginal costs on optimal HPV vaccination strategies

AbstractThe effectiveness of vaccinating males against the human papillomavirus (HPV) remains a controversial subject. Many existing studies conclude that increasing female coverage is more effective than diverting resources into male vaccination. Recently, several empirical studies on HPV immunization have been published, providing evidence of the fact that marginal vaccination costs increase with coverage. In this study, we use a stochastic agent-based modeling framework to revisit the male vaccination debate in light of these new findings. Within this framework, we assess the impact of coverage-dependent marginal costs of vaccine distribution on optimal immunization strategies against HPV. Focusing on the two scenarios of ongoing and new vaccination programs, we analyze different resource allocation policies and their effects on overall disease burden. Our results suggest that if the costs associated with vaccinating males are relatively close to those associated with vaccinating females, then coverage-dependent, increasing marginal costs may favor vaccination strategies that entail immunization of both genders. In particular, this study emphasizes the necessity for further empirical research on the nature of coverage-dependent vaccination costs

Utility Scores and Treatment Preferences for Clinical Early-Stage Cervical Cancer

AbstractObjectivesTo determine utility scores for health states relevant to the treatment of early-stage, high-risk cervical cancer.MethodsSeven descriptive health states incorporating the physical and emotional aspects of medical treatment, recovery, and prognosis were developed. Forty-five female volunteers valuated each health state using the visual analogue score (VAS) and time trade off (TTO) methods. Treatment options were ranked by mean and median TTO scores. The 95% confidence intervals were calculated to determine the statistical significance of ranking preferences. The Wilcoxon rank-sum test was used to compare central tendencies related to age, race, parity, and subject history of abnormal cervical cytology.ResultsVAS and TTO scores were highly correlated. Volunteers ranked minimally invasive radical hysterectomy with low-risk features as most preferred (mean TTO = 0.96; median TTO = 1.00) and aborted radical hysterectomy followed by chemoradiation as least preferred (mean TTO = 0.69; median TTO = 0.83). Health states that included radical surgery were ranked higher than those that included chemoradiation, either in the adjuvant or primary setting. When survival was comparable, volunteers rated radical hysterectomy with high-risk pathology followed by adjuvant chemoradiation (mean TTO = 0.78; median TTO = 0.92; 95% CI: 0.69–0.87) similarly to chemoradiation alone (mean TTO = 0.76; median TTO 0.90; 95% CI: 0.66–0.86; p = NS). Utility scores for the majority of health states were not significantly associated with age, race, parity, or subject history of abnormal cervical cytology.ConclusionSubjects consistently preferred surgical excision to treat early-stage, high-risk cervical cancer and chose a minimally invasive approach. Such utility scores can be used to incorporate quality-of-life effects into comparative-effectiveness models for cervical cancer

Impact of a Routine, Opt-Out HIV Testing Program on HIV Testing and Case Detection in North Carolina Sexually Transmitted Disease Clinics

The impact of routine, opt-out HIV testing programs in clinical settings is inconclusive. The objective of this study was to estimate the impact of an expanded, routine HIV testing program in North Carolina sexually transmitted disease (STD) clinics on HIV testing and case detection

Clomiphene, Metformin, or Both for Infertility in the Polycystic Ovary Syndrome

Background The polycystic ovary syndrome is a common cause of infertility. Clomiphene and insulin sensitizers are used alone and in combination to induce ovulation, but it is unknown whether one approach is superior. Methods We randomly assigned 626 infertile women with the polycystic ovary syndrome to receive clomiphene citrate plus placebo, extended-release metformin plus placebo, or a combination of metformin and clomiphene for up to 6 months. Medication was discontinued when pregnancy was confirmed, and subjects were followed until delivery. Results The live-birth rate was 22.5% (47 of 209 subjects) in the clomiphene group, 7.2% (15 of 208) in the metformin group, and 26.8% (56 of 209) in the combinationtherapy group (P\u3c0.001 for metformin vs. both clomiphene and combination therapy; P=0.31 for clomiphene vs. combination therapy). Among pregnancies, the rate of multiple pregnancy was 6.0% in the clomiphene group, 0% in the metformin group, and 3.1% in the combination-therapy group. The rates of first-trimester pregnancy loss did not differ significantly among the groups. However, the conception rate among subjects who ovulated was significantly lower in the metformin group (21.7%) than in either the clomiphene group (39.5%, P=0.002) or the combinationtherapy group (46.0%, P\u3c0.001). With the exception of pregnancy complications, adverse-event rates were similar in all groups, though gastrointestinal side effects were more frequent, and vasomotor and ovulatory symptoms less frequent, in the metformin group than in the clomiphene group. Conclusions Clomiphene is superior to metformin in achieving live birth in infertile women with the polycystic ovary syndrome, although multiple birth is a complication. (ClinicalTrials.gov number, NCT00068861.

Prevalence, incidence, and natural history of HPV infection in adult women ages 24 to 45 participating in a vaccine trial

Objectives The natural history of human papillomavirus (HPV) infection has been studied extensively in young women; this study investigated HPV infection in adult women. Methods Data from 3817 women aged 24–45 years in a global trial of the 4-valent HPV (6/11/16/18) vaccine were used to calculate prevalence of anogenital infections containing 9-valent (9v) HPV vaccine types (6/11/16/18/31/33/45/52/58) and five non-vaccine types (35/39/51/56/59). Incidence of infections and persistent infections was estimated for 989 placebo recipients naive to all 14 HPV types at baseline. Age-adjusted hazard ratios were calculated for various sociodemographic factors. Results Prevalence of anogenital infection was highest in France at 29.2% (9vHPV types) and 21.7% (non-vaccine types) and lowest in the Philippines at 7.6% (9vHPV types) and 5.1% (non-vaccine types). Overall, HPV incidence (per 100 person-years) was 5.2 (9vHPV types) and 4.7 (non-vaccine types), and incidence of persistent infection was 2.7 (9vHPV types) and 2.1 (non-vaccine types). Factors associated with new HPV infections included younger age, younger age at first intercourse, being single, current use of tobacco, and higher number of past and recent sex partners. Conclusions Because mid-adult women acquire new HPV infections, administration of the 9vHPV vaccine could reduce HPV-related morbidity and mortality in this population

Nicotine Replacement and Behavioral Therapy for Smoking Cessation in Pregnancy

This study examines whether adding nicotine replacement therapy (NRT) to cognitive behavioral therapy (CBT) for pregnant smokers increases rates of smoking cessation

Potential Impact of Antiretroviral Therapy and Screening on Cervical Cancer Mortality in HIV-Positive Women in Sub-Saharan Africa: A Simulation

Despite having high cervical cancer incidence and mortality rates, screening for cervical precancerous lesions remains infrequent in sub-Saharan Africa. The need to screen HIV-positive women because of the higher prevalence and faster progression of cervical precancerous lesions may be heightened by the increased access to highly-active antiretroviral therapy (HAART). Policymakers need quantitative data on the effect of HAART and screening to better allocate limited resources. Our aim was to quantify the potential effect of these interventions on cervical cancer mortality.We constructed a Markov state-transition model of a cohort of HIV-positive women in Cameroon. Published data on the prevalence, progression and regression of lesions as well as mortality rates from HIV, cervical cancer and other causes were incorporated into the model. We examined the potential impact, on cumulative cervical cancer mortality, of four possible scenarios: no HAART and no screening (NHNS), HAART and no screening (HNS), HAART and screening once on HAART initiation (HSHI), and HAART and screening once at age 35 (HS35). Our model projected that, compared to NHNS, lifetime cumulative cervical cancer mortality approximately doubled with HNS. It will require 262 women being screened at HAART initiation to prevent one cervical cancer death amongst women on HAART. The magnitudes of these effects were most sensitive to the rate of progression of precancerous lesions.Screening, even when done once, has the potential of reducing cervical cancer mortality among HIV-positive women in Africa. The most feasible and cost-effective screening strategy needs to be determined in each setting