Outcomes of screening to prevent cancer: analysis of cumulative incidence of cervical abnormality and modelling of cases and deaths prevented.

OBJECTIVE: To determine the frequency of different outcomes in women participating in cervical screening. DESIGN: Analysis of screening records from 348 419 women, and modelling of cases of cervical cancer and deaths with and without screening. SETTING: Cervical screening programme in Bristol. RESULTS: For every 10 000 women screened from 1976 to 1996, 1564 had abnormal cytology, 818 were investigated, and 543 had abnormal histology. One hundred and seventy six had persistent abnormality for two years or more. In the absence of screening 80 women would be expected to develop cancer of the cervix by 2011, of whom 25 would die. With screening 10 of these deaths would be avoided. Comparison of cumulative abnormality rates with numbers expected to develop cancer in the absence of screening suggests that at least 80% of high grade dyskaryosis and of high grade dysplasia would not progress to cancer. The lifetime risk of having abnormal cytology detected could be as high as 40% for women born since 1960. CONCLUSIONS: Screening is labour and resource intensive. It involves treatment for many women not destined to develop invasive cancer. The increased intervention rate for cervical abnormality in England is due to change in practice, not a cohort effect, and is probably the reason for the marked fall in incidence and mortality during the 1990s. For other cancers there is scope for major iatrogenic harm from screening because of invasive tests and treatments.

Environmental control and limnological impacts of a large recurrent spring bloom in Lake Washington, USA.

A series of statistical analyses were used to identify temporal and spatial patterns in the phytoplankton and nutrient dynamics of Lake Washington, an mesotrophic lake in Washington State (USA). These analyses were based on fortnightly or monthly samples of water temperature, Secchi transparency, ammonium (NH(4)), nitrate (NO(3)), inorganic phosphorus (IP), total nitrogen (TN), total phosphorus (TP), dissolved oxygen (DO), pH and chlorophyll a (chl a) collected during 1995-2000 from 12 stations. Lake Washington has a very consistent and pronounced annual spring diatom bloom which occurs from March to May. During this bloom, epilimnetic chl a concentrations peak on average at 10 microg/L, which is 3 times higher than chl a concentrations typically seen during summer stratified conditions. The spring bloom on average comprised 62% diatoms, 21% chlorophytes and 8% cyanobacteria. During summer stratification, diatoms comprised 26% of the phytoplankton community, chlorophytes 37% and cyanobacteria 25%. Cryptophytes comprised approximately 8% of the community throughout the year. Overall, 6 phytoplankton genera (i.e., Aulacoseira, Fragilaria, Cryptomonas, Asterionella, Stephanodiscus, and Ankistrodesmus) cumulatively accounted for over 50% of the community. These analyses also suggest that the phytoplankton community strongly influences the seasonality of NO(3), IP, DO, pH and water clarity. According to a MANOVA, seasonal fluctuations explained 40% of the total variability for the major parameters, spatial heterogeneity explained 10% of variability, and the seasonal-spatial interaction explained 10% of variability. Distinctive patterns were identified between offshore and inshore sampling stations. The results of our analyses also suggest that spatial variability was substantial, but much smaller than temporal variability.

Inorganic-organic interpenetrating frameworks: 4,4'-bipyridine N,N'-dioxide as a bridging hydrogen-bond acceptor.

4,4'-Bipyridine N,N'-dioxide (L) acts as a hydrogen-bond acceptor in the compounds ([M(NO3)2(H2O)4].L2) (M = Co, Ni) to form doubly-interpenetrated framework materials with sixfold topological connectivity.

Outcome of women referred to colposcopy for persistently inadequate smears.

The outcome of referral to colposcopy of 240 women who had persistently inadequate smears was investigated. Of 232 women who attended colposcopy, 214 (92.2%) had a normal outcome, 12 (5.2%) had low grade abnormalities, and six (2.6%) had high grade abnormalities. This group of women therefore has a negligibly increased risk of harbouring cervical neoplasia. Although not directly comparable, women with a history of previous abnormal cytology did not have a higher risk than those without such a history. Unnecessary colposcopy could have been avoided in the majority of cases if a good quality repeat smear had been taken. Improved smear taker training could decrease the number of referrals. A hospital cytology clinic is proposed as a cost-effective alternative to colposcopy at the first attendance.

A highly unsaturated fatty acid predicts carbon transfer between primary producers and consumers.

The factors that regulate energy transfer between primary producers and consumers in aquatic ecosystems have been investigated for more than 50 years. Among all levels of the food web (plants, herbivores, carnivores), the plant-animal interface is the most variable and least predictable link. In hypereutrophic lakes, for example, biomass and energy transfer is often inhibited at the phytoplankton-zooplankton link, resulting in an accumulation of phytoplankton biomass instead of sustaining production at higher trophic levels, such as fish. Accumulation of phytoplankton (especially cyanobacteria) results in severe deterioration of water quality, with detrimental effects on the health of humans and domestic animals, and diminished recreational value of water bodies. We show here that low transfer efficiencies between primary producers and consumers during cyanobacteria bloom conditions are related to low relative eicosapentaenoic acid (20:5omega3) content of the primary producer community. Zooplankton growth and egg production were strongly related to the primary producer 20:5omega3 to carbon ratio. This indicates that limitation of zooplankton production by this essential fatty acid is of central importance at the pelagic producer-consumer interface.

A case-control study of true-positive versus false-negative cervical smears in women with cervical intraepithelial neoplasia (CIN) III.

Cervical smears (n = 150) from five departments showing high-grade dyskaryosis were examined by three cytologists. All the smears came from patients with biopsy-proven CIN III. One hundred had been correctly reported (true positives) but 50 had originally been reported as negative and had been found to be positive only on review (false negatives). There were significant differences between the two sets in the characteristics of the dyskaryotic cell population. The false-negative smears tended to have fewer than 200 dyskaryotic cells. The nuclei of the dyskaryotic cells tended to have fine rather than coarse nuclear chromatin. A smear with fewer than 50 dyskaryotic cells is 26 times more likely to be reported as negative than one with more than 200 dyskaryotic cells. The results suggest that there is a type of severely dyskaryotic smear that is inherently likely to be missed on routine screening.

A meta-analysis of the freshwater trophic cascade.

The generality of the trophic cascade has been an intensely debated topic among ecologists. We conducted a meta-analysis of 54 separate enclosure and pond experiments that measured the response of the zooplankton and phytoplankton to zooplanktivorous fish treatments. These results provide unequivocal support for the trophic cascade hypothesis in freshwater food webs. Zooplanktivorous fish treatments resulted in reduced zooplankton biomass and increased phytoplankton biomass. The trophic cascade was weakly dampened at the level of the phytoplankton. However, the response of the phytoplankton to the trophic cascade was highly skewed, with very strong responses in slightly more than one-third of the cases and weak responses in the others.

Caecal perforation in a renal transplant patient with disseminated histoplasmosis.

A renal transplant patient developed a fatal caecal perforation after Histoplasma capsulatum infection acquired abroad. Disseminated histoplasmosis is an uncommon fungal infection, usually seen in patients with impaired immunity. The diagnosis should be considered in immunosuppressed patients who develop prolonged fever or whose health deteriorates unexpectedly after travelling overseas. The infection is endemic in parts of the United States of America but occurs all over the world. Rapid diagnosis is often possible by histological examination of infected tissues. Treatment if started early may lead to recovery, but if it is not treated it is usually fatal.