Study of physical function in adolescents with haemophilia: The SO-FIT study

INTRODUCTION

Contemporary haemophilia care demands Patient-Reported Outcomes. SO-FIT is a UK multi-centre study, assessing self-reported function, health-related quality of life (HRQoL) and joint health in boys with severe haemophilia.

METHODS

Subjective physical function (PedHAL, HEP-Test-Q) and HRQoL (Haemo-QoL Short Form [SF]) were assessed alongside joint health using the objective Haemophilia Joint Health Score (HJHS v2.1). Demographic and clinical data were collected.

RESULTS

Data from 127 boys mean age 12.38 ± 2.5 (range 8-17) treated at 16 sites were analysed. One-hundred-and-thirteen had haemophilia A, 25/9 past/current inhibitor, 124 were treated prophylactically (46.8% primary) and three on-demand. In the preceding 6 months, boys reported median 0 joint bleeds (range 0-8) with a median HJHS score of 1 (range 0-30). Boys reported good physical functioning; HEP-Test-Q (M = 80.32 ± 16.1) showed the highest impairments in the domain "endurance" (72.53 ± 19.1), in PedHAL (M = 85.44 ± 18.9) highest impairments were in the domains "leisure activities & sports" (M = 82.43 ± 23.4) and "lying/sitting/kneeling/standing" (M = 83.22 ± 20.3). Boys reported generally good HRQoL in Haemo-QoL SF SF (M = 22.81 ± 15.0) with highest impairments in the domains "friends" (M = 28.81 ± 30.5) and "sports & school" (M = 26.14 ± 25.1). HJHS revealed low correlations with the Haemo-QoL SF (r = .251, P < .006), the PedHAL (r = -.397, P < .0001) and the HEP-Test-Q (r = -.323, P < .0001). A moderate correlation was seen between HEP-Test-Q and Haemo-QoL SF of r = -.575 (P < .0001) and between PedHAL and Haemo-QoL SFr = -.561 (P < .0001) implying that good perceived physical function is related to good HRQoL.

CONCLUSIONS

The SO-FIT study has demonstrated that children with severe haemophilia in the UK report good HRQoL and have good joint health as reflected in low HJHS scores.

Carrier testing in haemophilia A and B: adult carriers' and their partners' experiences and their views on the testing of young females

This is a descriptive study, which aims to report adult carriers' and their husbands/partners' experiences of carrier diagnosis and their views as to how these issues should be handled for the next generation. Following an initial pilot, 105 carriers and husbands/partners responded to a postal questionnaire. Most of the adult carriers had been tested because either they or their parents wanted to know their carrier status or they had a son diagnosed with haemophilia. The respondents agreed that the main reasons for testing young potential carriers should be either a family history of severe haemophilia or that the young person or her parents wanted to know her status. Forty per cent (35/87) believed the earliest age for carrier testing should be 0-9 years, 44% (38/87) 10-15 years and 16% (14/87) > or =16 years. Respondents aged 18-39 years were more likely to be in favour of testing <2 years. If parents and teenagers disagreed, the majority of parents thought that a test should not be forced, consent refused or results withheld. Genetic counselling provides an important opportunity for parents, who want a very early genetic test, to explore their motivations and balance their desire to prepare and protect their daughter with her right to decide as a teenager.

Antiviral therapy for chronic hepatitis C in patients with inherited bleeding disorders: an international, multicenter cohort study

BACKGROUND

Hepatitis C is a major co-morbidity in patients with hemophilia. However, there is little information on the efficacy of antiviral therapy and long-term follow-up after treatment.

OBJECTIVES

To assess the effect of interferon-based (IFN-based) therapy on hepatitis C virus (HCV) eradication, to identify determinants associated with treatment response, and to assess the occurrence of end-stage liver disease (ESLD) after completing antiviral therapy.

PATIENTS AND METHODS

In a multicenter cohort study, 295 treatment-naïve hemophilia patients chronically infected with HCV were included. The effect of therapy was expressed as sustained virological response (SVR). Determinants associated with treatment response were expressed as odds ratios (ORs). Cumulative incidence of ESLD was assessed using a Kaplan-Meier survival table.

RESULTS

Among human immunodeficiency virus (HIV) negative patients (n = 235), SVR was 29% (29/101) for IFN monotherapy, 44% (32/72) for IFN with ribavirin, and 63% (39/62) for pegylated IFN (PegIFN) with ribavirin. In patients co-infected with HIV (n = 60), IFN monotherapy, IFN with ribavirin, and PegIFN with ribavirin eradicated HCV in 7/35 (20%), 1/2 (50%), and 11/23 (48%), respectively. SVR increased with genotype 2 and 3 [OR 11.0, 95% CI: 5.8-20.5], and combination therapy (IFN and ribavirin OR 3.7, 95% CI: 1.7-8.4), PegIFN and ribavirin (OR 4.2, 95% CI: 1.8-9.5). Up to 15 years after antiviral treatment, none of the patients with a SVR relapsed and none developed ESLD. In contrast, among unsuccessfully treated patients the cumulative incidence of ESLD after 15 years was 13.0%.

CONCLUSIONS

Successful antiviral therapy appears to have a durable effect and reduces the risk of ESLD considerably.

Experience of prophylaxis treatment in children with severe haemophilia

The practice of prophylactic treatment of boys with severe haemophilia has been evaluated in our centre. Prophylaxis was started at the median age of 3.7 years (range 0.4-12.7 years) in 38/41 children (93%) under 17 years of age. Median follow-up was 4.1 years (range 0.4-12.7 years). The criteria of primary prophylaxis according to the definition by the European Paediatric Network of Haemophilia Management was fulfilled by 9/38 (24%). Although a majority [76%, 29/38] of the children started prophylaxis after a median number of joint bleeds of 3.5, 70% of the children in this group had clinical joint scores of 0. Intravenous catheter insertion was required at a median age of 15.5 months (range 5-36 months) in 21% of the children, resulting in a catheter infection rate of 1.74 per 1000 catheter days. None developed an inhibitor on prophylaxis and three patients who had low-titre inhibitors (< 5 Bethesda units) prior to prophylaxis had undetectable inhibitors after prophylaxis. The home-treatment training programme required considerable time and cost. As a result, 87% of the children used peripheral venous access and hospital visits declined as prophylaxis became established. Parents' incentives for prophylaxis were that the children undertook many physical activities and sports previously not recommended, there was less parental anxiety and an overall improvement in the quality of life for the whole family.

Retrospective review of the management of elective surgery with desmopressin and clotting factor concentrates in patients with von Willebrand disease

Limited data are available regarding optimal treatment with desmopressin (DDAVP) or intermediate-purity FVIII concentrates rich in VWF (CFCs) in patients with von Willebrand disease (VWD) who undergo planned surgery. We undertook a retrospective review over 10 years (1988-1997) and identified 27 patients treated with DDAVP for 35 surgical events and 38 patients who received CFCs for 68 elective surgical events. Tranexamic acid was usually added for mucosal surgery. The FVIII:C levels and the severity of surgery were used to determine the frequency and the doses of postoperative treatment. For major surgery the median pre- and post-operative doses of CFCs were 54 and 43 IU/kg, respectively, and for minor surgery the median doses varied between 34 and 52 IU/kg preoperatively and between 23 and 37 IU/kg postoperatively. The effectiveness of haemostasis was excellent in 32 events (91%) treated with DDAVP and in 56 events (82%) treated with CFCs. It is concluded that patients with VWD do not carry an increased operative risk if appropriate therapy is given.

The natural history of HCV in a cohort of haemophilic patients infected between 1961 and 1985

AIM

This study describes the long term follow up of haemophilic patients infected with hepatitis C virus (HCV) between 1961 and 1985.

METHODS

Clinical and treatment records from 310 patients with inherited coagulation disorders treated with blood product before 1985 were reviewed. Standard survival analysis methods were used to model progression to liver failure and death.

RESULTS

A total of 298/305 (98%) patients tested were anti-HCV positive. Twenty seven (9%) individuals consistently HCV polymerase chain reaction negative were considered to have cleared the virus. By 1 September 1999, 223/310 (72%) were alive, 26 (8%) had died a liver related death, and 61 (20%) had died from other, predominantly human immunodeficiency virus (HIV) related, causes. Kaplan-Meier progression rates to death from any cause and liver related deaths 25 years after exposure to HCV were 47% (95% confidence intervals (CI) 34-60) and 19% (95% CI 10-27), respectively. After 13.3 years from 1985, by which time all patients had seroconverted to HIV, progression rates to death from any cause and liver related deaths were, respectively, 8% (95% CI 4-13) and 3% (95% CI 0.4-6) for those HIV negative, and 57% (95% CI 48-66) and 21% (95% CI 13-31) for those HIV positive (p=0.0001). Using Cox proportional hazard models, the adjusted relative hazard of death for individuals coinfected with HIV compared with those infected with HCV alone was 19.47 (95% CI 9.22-41.10), 0.99 (95% CI 0.39-2.53), 3.47 (95% CI 1.40-8.63), and 9.74 (95% CI 3.91-24.26) for the age groups at infection 10-19 years, 20-29 years, and >30 years, respectively, compared with the age group <10 years. The adjusted relative hazard for genotype 1 compared with other genotypes was 2.7 (95% CI 1.36-5.15).

CONCLUSIONS

While 25 year follow up of 310 haemophilic patients has shown the potentially lethal combination of HIV and HCV coinfection, HCV singly infected individuals show slow progression of liver disease.

Two decades of HIV infection in a cohort of haemophilic individuals: clinical outcomes and response to highly active antiretroviral therapy

OBJECTIVES

Many haemophilic individuals infected with HIV died before receiving antiretroviral therapy (ART). Most who remain alive are chronically infected with hepatitis C virus (HCV), which has implications for their prognosis and choice of ART. The clinical status of a cohort of HIV-positive haemophilic men is reported together with their response to highly active antiretroviral therapy (HAART).

DESIGN

Longitudinal cohort study.

SETTING

A comprehensive care haemophilia centre.

PATIENTS

A group of 111 haemophilic men who seroconverted to HIV in the period 1979 to 1985.

RESULTS

The cohort has been followed since 1979. By 30 April 1999, 57 of the 111 men had developed AIDS and 65 had died: Kaplan-Meier rates of 57.0% [95% confidence interval (CI) 46.9-67.0) and 65.1% (95% CI 52.7-77.4) by 19.5 years, respectively. AIDS rates have declined since 1997 but death rates have remained high, largely owing to deaths from non-HIV-related causes. Thirty-five patients remain alive and under follow-up at the clinic. The 28 men who had received ART had lower CD4 cell counts than the seven patients who had not received ART, but the two groups were otherwise similar. In total, 21 patients are known to have started HAART while under care at the centre. By 10-12 months after starting HAART, viral loads dropped by 2.06 log10 copies/ml and CD4 cell counts increased by 60 x 10(6) cells/l. In 10 out of 18 patients with viral loads initially > 400 copies/ml, a viral load below this level was attained; four had changed therapy at the time.

CONCLUSIONS

While the decision to initiate HAART in haemophilic men should be made carefully because of the possible adverse events, our results suggest that a good response rate was achieved in this group of men.

Type 1 von Willebrand disease - a clinical retrospective study of the diagnosis, the influence of the ABO blood group and the role of the bleeding history

This clinical retrospective study investigated the difficulties in diagnosing type 1 von Willebrand disease (VWD). A total of 246 patients previously diagnosed with type 1 VWD were reclassified into 'possible' type 1 VWD (patients with low levels of VWF adjusted for the blood group and either a significant bleeding history or family history) and 'definite' type 1 VWD, requiring low levels of von Willebrand factor (VWF), a bleeding history and inheritance. On reclassification, only 144/246 (59%) patients had low VWF levels adjusted for blood group, 88/246 (36%) patients met all the criteria for 'definite' type 1 VWD and 51/246 (21%) patients were 'possible' type 1 VWD. A significant proportion of patients, 102/246 (42%), remained an indeterminate group with blood type O, VWF levels between 35 and 50 U/dl and personal and/or family bleeding history. This subgroup might require reclassification as 'not VWD'. However, a similar bleeding tendency was found in two matched groups of patients of blood groups O and non-O and VWF levels between 35 and 50 U/dl. These results suggest that the use of ABO adjusted ranges for VWF levels might not be essential for diagnosis, because bleeding symptoms may depend on the VWF level regardless of the ABO type. Of the diagnostic criteria, the bleeding history was of prime importance in the clinical decision to diagnose and treat type 1 VWD. These observations could help in the reconsideration of how the criteria for diagnosing type 1 VWD could be adjusted in order to maximize their clinical relevance.

Demographic, clinical and social factors associated with human immunodeficiency virus infection and other sexually transmitted diseases in a cohort of women from the United Kingdom and Ireland. MRC Collaborative Study of women with HIV

BACKGROUND

Clinical experience suggests many women with HIV infection have experienced no other sexually transmitted diseases (STD). Our objective was to test the hypothesis that a substantial proportion of women with HIV infection in the United Kingdom and Ireland have experienced no other diagnosed STD and to describe the demographic, clinical and social factors associated with the occurrence of other STD in a cohort of HIV infected women.

METHOD

Analysis of cross-sectional baseline data from a prospective study of 505 women with diagnosed HIV infection. The setting was 15 HIV treatment centres in the United Kingdom and Ireland. The main outcome measures were occurrence of other STD diagnosed for the first time before and after HIV diagnosis. Data were obtained from interview with women and clinic notes. We particularly focused on occurrence of gonorrhoea, chlamydia and trichomoniasis after HIV diagnosis, as these are the STD most likely to reflect recent unprotected sexual intercourse.

RESULTS

The women were mainly infected via heterosexual sex (n = 304), and injection drug use (n = 174). 151 were black Africans. A total of 250 (49.5%) women reported never having been diagnosed with an STD apart from HIV, 255 (50.5%) women had ever experienced an STD besides HIV, including 109 (21.6%) who had their first other STD diagnosed after HIV. Twenty-five (5%) women reported having had chlamydia, gonorrhoea or trichomoniasis diagnosed for the first time after HIV diagnosis, possibly reflecting unprotected sexual intercourse since HIV diagnosis. In all 301 (60%) women reported having had sex with a man in the 6 months prior to entry to the study. Of these, 168 (58%) reported using condoms 'always', 66(23%) 'sometimes' and 56 (19%) 'never'.

CONCLUSIONS

Half the women in this study reported having never experienced any other diagnosed STD besides HIV. However, after HIV diagnosis most women remain sexually active and at least 5% had an STD diagnosed which reflect unprotected sexual intercourse.

Influence of HIV-1 infection on GBV-C infection in multiply infected haemophilic patients

Two hundred thirteen haemophilic patients were studied for the presence of GBV-C RNA and anti-E2 antibodies soon after their first treatment with unsterilised factor concentrates and in their most recent sample. An assessment was made to determine whether coinfection with HIV had any effect on the progression of GBV-C infection. All of the patients were infected with HCV and 81 patients (37%) were also infected with HIV. GBV-C RNA was detected using the Abbott LCx(TM) assay and by RT-PCR. Anti-E2 antibodies were detected using the microPLATE Anti-HGenv assay and by Abbott Laboratories. The HIV-negative patients were more likely than the HIV-positive patients to lose GBV-C RNA between the two time points. A proportion of the patients lost their anti-E2 antibodies over the time period, however, the majority of these were HIV-positive. This study shows that infection with HIV does affect the progression of GBV-C infection, however, this effect is little understood as yet.

The relationship of HIV prevalence in pregnant women to that in women of reproductive age: a validated method for adjustment

OBJECTIVE

To devise and validate a method for adjusting HIV seroprevalences in pregnant women to estimate population prevalences among all women in their child-bearing years.

DESIGN

Birth and termination rates from women with known HIV infection in the United Kingdom were calculated according to the likely route of HIV infection and whether HIV infection was diagnosed.

METHODS

Birth and termination rates were weighted and combined to produce summary statistics. Comparisons were then made with population birth and termination rates to derive summary relative inclusion ratios (RIRs), the relative probabilities of including HIV-infected and uninfected women in seroprevalence surveys of pregnant women.

RESULTS

The derived RIRs for women having live births were close to unity: 1.03 [95% confidence intervals (CI) 0.90-1.17] for London and 0.80 (Cl, 0.71-0.89) for elsewhere in England and Wales. This indicates that currently observed overall seroprevalences among pregnant women having live births in London would be similar to those among all women of the same age, while elsewhere it would be slightly underestimated. Sensitivity analysis indicated that RIRs could, however, vary three-fold (0.47-1.56) according to the proportion of diagnosed maternal infections and the mix of maternal HIV-exposure categories. The method was validated by using it to predict the ratio of unlinked seroprevalences between women having terminations and live births in London. It predicted a ratio of 1.74: 1, which is close to the observed ratio of 2.07 : 1.

CONCLUSIONS

Application of HIV seroprevalences from pregnant women to whole populations may need adjustment for fertility rates among HIV-infected women. A general method for this has been derived and validated. Gathering fertility data for HIV-infected women is a useful adjunct to serosurveillance.

The effect of HIV diagnosis on reproductive experience. Study Group for the Medical Research Council Collaborative Study of Women with HIV

OBJECTIVES

To compare rates of reproductive events before and after HIV diagnosis in a cohort of women with HIV infection, and to consider the impact of HIV diagnosis on the outcome of pregnancy.

DESIGN

Observational cohort study of 503 women recruited from 15 genitourinary medicine/HIV clinics in Britain and Ireland. The 503 women had 580 pregnancies before diagnosis of HIV infection and 202 after HIV diagnosis.

METHODS

Using date of birth, date of HIV diagnosis, the outcome of all lifetime pregnancies and date of each outcome, age-specific rates (per 100 women-years) of pregnancy, miscarriage, termination and live-birth were calculated before HIV diagnosis, and separately after HIV diagnosis. Rates after HIV diagnosis were age-standardized for comparison with rates before HIV diagnosis. Rates were also calculated separately by ethnic group and HIV transmission group.

RESULTS

In women aged 20-34 years, the age-adjusted live-birth rate fell by 44% from 10.2 [95% confidence interval (CI), 9.2-11.2] per 100 women-years before HIV diagnosis to 5.7 (95% CI, 4.3-7.1) after diagnosis. Most of the decline reflected an increase in termination rate from 3.5 (95% CI, 2.9-4.1) before HIV diagnosis to 6.3 (95% CI, 4.7-7.9) after diagnosis. A decline in live-births together with a rise in termination after HIV diagnosis was a consistent finding across age and ethnic groups. However, black African women had the smallest reduction in live-births, despite the greatest increase in termination, because the pregnancy rate increased after HIV diagnosis in this group.

CONCLUSIONS

Diagnosis of HIV infection in women has a substantial impact in reducing live-birth rates. These findings have important implications for expanding HIV testing in women. They highlight the need for better understanding of reproductive decision-making in the context of HIV infection and better contraceptive support for HIV-infected women and their partners.

Uptake of medical interventions in women with HIV infection in Britain and Ireland. Study Group for the MRC Collaborative Study of HIV Infection in Women

OBJECTIVE

To determine the uptake of medical interventions amongst women known to be HIV positive and in contact with service providers.

SUBJECTS

400 HIV positive women from 15 STD/HIV clinics in Britain and Ireland recruited to the MRC collaborative study of HIV infection in women between June 1992 and August 1994.

METHODS

Data obtained prospectively through direct questioning of all women by a physician or research nurse and review of medical and laboratory records. Data recorded on standardised forms and analysed centrally.

RESULTS

Nearly one quarter (24%) of women with an AIDS diagnosis had never received Pneumocystis carinii pneumonia prophylaxis, and 24% had never received any antiretroviral therapy. Fewer than two-thirds of black African women had had a chest radiograph. Only one woman had received Pneumovax and only 4% of women had ever taken part in a clinical trial.

CONCLUSIONS

A substantial proportion of women with HIV infection did not receive interventions of proven benefit, and participation in clinical trials was very uncommon. The reasons for such poor uptake should be explored among both health care workers and women with HIV infection.

Ethnic differences in women with HIV infection in Britain and Ireland. The study group for the mrc collaborative study of HIV infection in women

OBJECTIVE

To examine ethnic differences in the socio-epidemiological and clinical characteristics of a cohort of women with HIV infection in Britain and Ireland.

DESIGN AND METHODS

Analysis of baseline data (ethnic group, sexual history, likely route of HIV infection, reasons for HIV testing and first AIDS-defining disease) from 400 women with HIV infection recruited into a cohort study from 15 genitourinary medicine/HIV clinics in Britain and Ireland.

RESULTS

Sixty-five per cent of women were white and 29% black African. Their median number of lifetime sexual partners was seven and three, respectively (P < 0.001). Ninety-three per cent of black African and 43% of white women were probably infected through sexual intercourse. Injecting drug use was the most likely route of infection in 55% of white women, but none of the black African women. Perceived risk (33%) or investigation of symptoms (26%) were the most common reasons for HIV testing. Seven per cent of white women and 16% of black African women (P < 0.001) had AIDS when HIV infection was diagnosed. The distribution of first AIDS-defining diagnoses differed (P = 0.001) by ethnic group. For white women, the most common disease was Pneumocystis carinii pneumonia; for black African women it was pulmonary tuberculosis.

CONCLUSION

There are important differences between black African and white women in sexual history and route of transmission, disease stage at diagnosis and pattern of AIDS-defining diseases.

Usefulness of a non-experimental study design in the evaluation of service developments for infant feeding in a general hospital

There are likely to be many situations in which it is not possible to use a randomized controlled trial (RCT) for the evaluation of local service developments, and the usefulness of non-experimental study designs need to be assessed. This is examined with reference to a study carried out to evaluate the appointment of a baby feeding adviser (BFA) and other policy changes for infant feeding at a district general hospital (DGH). Surveys of Maternity Unit staff attitudes and practices, and of mothers' experiences were carried out in 1988 (prior to the changes) and afterwards in 1990. Service changes were; appointment of a BFA, removal from the postnatal wards of dextrose, seminars on baby feeding for midwifery staff, and a reduction of night-only shifts. There was no change in the initial breast feeding rate of about 80%, but there was an increase in breast feeding at 6 weeks postnatally from 57% (95% CI; 51-64) to 64% (95% CI; 59-69); P = 0.15. The percentage of women who stopped breast feeding by 6 weeks fell from 30% in 1988 to 22% in 1990; P = 0.11. Mothers who did not see the BFA (1990 only) were significantly less likely to begin breast feeding (P = 0.03), independent of social class and age, but a similar association was not seen at 6 weeks. There were significant reductions in the percentage of midwifery staff viewing feeding policy as unimportant (P = 0.02), and in the use of supplements for breast-fed babies (P < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

CD44 splice variants: expression during lymphocyte activation and tumor progression

A recently described splice variant of CD44 has been shown to confer metastatic potential to non-metastasizing rat pancreatic carcinoma and sarcoma cell lines. Using antibodies raised against a bacterial fusion protein encoded by variant CD44 sequences, we have explored the expression of variant CD44 glycoproteins in human lymphoid cells and tissues, in non-Hodgkin's lymphomas, and in colorectal neoplasia. Normal lymphohematopoietic cells express barely detectable low levels of variant CD44 glycoproteins, while T lymphocytes, upon activation by mitogen or antigen, transiently upregulate expression of specific CD44 variant glycoproteins. The reaction pattern of various antibodies indicates that these CD44 variants contain the domain encoded by exon v6, which is part of the variant that in the rat confers metastatic capability. Interestingly, overexpression of v6 was also found in several aggressive, but not in low-grade, non-Hodgkin's lymphomas (NHL). In human colorectal neoplasia we also observed strong overexpression of CD44 splice variants in all invasive carcinomas and carcinoma metastasis. Interestingly, focal expression was already observed in adenomatous polyps, expression being related to areas of dysplasia. The findings establish CD44 variants as tumor progression markers in colorectal cancer.

An antigen expressed by murine CD8+ T cells and activated B cells

A monoclonal antibody, H1F5, is described that reacts with a subset of Lyt-2 (CD8) mouse T cells and LPS-activated B cells. In both lymph nodes and spleen of BALB/c mice, the H1F5 antigen is coexpressed approximately on 20%-30% of the CD8+ T cells and approximately on 91% of LPS-activated B cells. In the thymus, few cells (less than 1%) are positive for the marker, but no correlation could be demonstrated with markers for mature T cells such as MEL-14 and PNA expression. Elimination of H1F5+ cells by complement lysis led to a 30%-50% reduction of specific lysis as measured in a primary allo CTL, indicating that the cytotoxic effector cells are injured. The relationship of this marker and other antigenic determinants on lymphocytes is discussed.

Chemical and bacteriological composition of granular methanogenic sludge

Methanogenic sludge granules grown on waste water from a sugar refinery consisted of several bacterial morphotypes embedded in a matrix of extracellular material. Comparison of critical point drying and freeze-drying methods for preparing samples for scanning electron microscopy to determine the presence of extracellular material indicated that the former method permitted observations of extracellular material and intact cells. The effects of different extraction methods used for isolation of these extracellular polymers was also investigated by scanning electron microscopy. Of the various extraction procedures (EDTA, NaOH, autoclaving, water–phenol), water–phenol left most of the cells intact and was found to be a very efficient method of extraction. Extracellular polymers equivalent to 10–20 mg hexose/g of granules were extracted. The high resistance of the granules against disintegration by various chemical methods suggested that different extracellular polymers and probably different groups of organisms contributed to the matrix in which the bacteria were embedded. The chemical composition of the granules did not differ from the composition of bacteria in general. The buoyant density of 1.00–1.05 g∙g−1of the granules indicated that a simple agglomeration was the mechanism by which these methanogenic consortia improved their settling characteristics.