The levonorgestrel intrauterine system versus endometrial ablation for heavy menstrual bleeding: a cost-effectiveness analysis

Objective

To evaluate the costs and non‐inferiority of a strategy starting with the levonorgestrel intrauterine system (LNG‐IUS) compared with endometrial ablation (EA) in the treatment of heavy menstrual bleeding (HMB).

Design

Cost‐effectiveness analysis from a societal perspective alongside a multicentre randomised non‐inferiority trial.

Setting

General practices and gynaecology departments in the Netherlands.

Population

In all, 270 women with HMB, aged ≥34 years old, without intracavitary pathology or wish for a future child.

Methods

Randomisation to a strategy starting with the LNG‐IUS (n = 132) or EA (n = 138). The incremental cost‐effectiveness ratio was estimated.

Main outcome measures

Direct medical costs and (in)direct non‐medical costs were calculated. The primary outcome was menstrual blood loss after 24 months, measured with the mean Pictorial Blood Assessment Chart (PBAC)‐score (non‐inferiority margin 25 points). A secondary outcome was successful blood loss reduction (PBAC‐score ≤75 points).

Results

Total costs per patient were €2,285 in the LNG‐IUS strategy and €3,465 in the EA strategy (difference: €1,180). At 24 months, mean PBAC‐scores were 64.8 in the LNG‐IUS group (n = 115) and 14.2 in the EA group (n = 132); difference 50.5 points (95% CI 4.3–96.7). In the LNG‐IUS group, 87% of women had a PBAC‐score ≤75 points versus 94% in the EA group (relative risk [RR] 0.93, 95% CI 0.85–1.01). The ICER was €23 (95% CI €5–111) per PBAC‐point.

Conclusions

A strategy starting with the LNG‐IUS was cheaper than starting with EA, but non‐inferiority could not be demonstrated. The LNG‐IUS is reversible and less invasive and can be a cost‐effective treatment option, depending on the success rate women are willing to accept.

Tweetable abstract

Treatment of heavy menstrual bleeding starting with LNG‐IUS is cheaper but slightly less effective than endometrial ablation.

Treatment of heavy menstrual bleeding starting with LNG‐IUS is cheaper but slightly less effective than endometrial ablation.

Two-year effects and cost-effectiveness of pelvic floor muscle training in mild pelvic organ prolapse: a randomised controlled trial in primary care

OBJECTIVE

To compare effects and cost-effectiveness of pelvic floor muscle training (PFMT) and watchful waiting in women with pelvic organ prolapse.

DESIGN

Randomised controlled trial.

SETTING

Dutch general practice.

POPULATION

Women (≥55 years) with symptomatic mild prolapse, identified by screening.

METHODS

Linear multilevel analysis.

MAIN OUTCOME MEASURES

Primary outcome was change of pelvic floor symptoms (Pelvic-Floor-Distress-Inventory-20 [PFDI-20]) during 24 months. Secondary outcomes were condition-specific and general quality of life, costs, sexual functioning, prolapse stage, pelvic floor muscle function and women's perceived improvement of symptoms.

RESULTS

PFMT (n = 145) resulted in a 12.2-point (95% CI 7.2-17.2, P < 0.001) greater improvement in PFDI-20 score during 24 months compared with watchful waiting (n = 142). Participants randomised to PFMT more often reported improved symptoms (43% versus 14% for watchful waiting). Direct medical costs per person were €330 for PFMT and €91 for watchful waiting but costs for absorbent pads were lower in the PFMT group (€40 versus €77). Other secondary outcomes did not differ between groups. Post-hoc subgroup analysis demonstrated that PFMT was more effective in women experiencing higher pelvic floor symptom distress at baseline.

CONCLUSION

PFMT resulted in greater pelvic floor symptom improvement compared with watchful waiting. The difference was statistically significant, but below the presumed level of clinical relevance (15 points). PFMT more often led to women's perceived improvement of symptoms, lower absorbent pads costs, and was more effective in women experiencing higher pelvic floor symptom distress. Therefore, PFMT could be advised in women with bothersome symptoms of mild prolapse.

TWEETABLE ABSTRACT

Pelvic floor muscle training can be effective in women with bothersome symptoms of mild prolapse.

[Practice guideline 'Urinary incontinence in women' from the Dutch College of General Practitioners]

- The Dutch College of General Practitioners' (NHG) practice guideline 'Urinary incontinence in women' provides guidelines for diagnosis and management of stress, urgency and mixed urinary incontinence in adult women.- General practitioners (GPs) should be alert to signals for urinary incontinence in women and offer active diagnosis and treatment if necessary.- Shared decision making is central in the guideline; the GP and the patient should discuss therapeutic options and decide on treatment policy in mutual consultation.- Women with stress urinary incontinence can choose between pelvic floor exercises or a pessary as initial treatment. Placing a midurethral sling (MUS) will be discussed if initial treatment is insufficiently effective or in the case of serious symptoms.- When bladder training is ineffective in urgency incontinence, the GP will discuss the pros and cons of adding an anticholinergic agent.- Exercise therapy can take place in the GPs practice or under supervision of a pelvic physical therapist.

Transfer of information on palliative home care during the out-of-hours period

BACKGROUND

Continuity of end-of-life care for patients receiving palliative care is an important challenge for out-of-hours services in general practice.

AIM

To investigate how frequent information is transferred on patients receiving palliative care from GPs to the out-of-hours services, to explore the perceptions of GP's on this information transfer and to study the relation between information transfer and the used GP information systems.

METHODS

This is a mixed-method design study. The frequency of information transfer to the out-of-hours services was investigated by analyzing a regional out-of-hours database. Barriers and promoting factors for this transfer of information were investigated by using semi-structured interviews among a purposive sample of GPs from the same region. The relation between information transfer and the GP information system was investigated by a postal questionnaire in a national random selection of GPs.

RESULTS

When a palliative patient contacted the out-of-hours service, for 20% of these patients, a transfer of information was available and only half of these transfers included an anticipating end-of-life plan. All interviewed GPs considered continuity of care for these patients as important. However, some doubted whether a transfer of information is relevant for the quality of care. There was no relation between the information transfer and the used GP information systems.

CONCLUSION

For only a minority of patients receiving palliative care, a transfer of information including an anticipating management plan was present. There is a large variation in the opinions of GPs on how to organize continuity of end-of-life care.

[Summary of the practice guideline 'Vaginal discharge' (first revision) from the Dutch College of General Practitioners]

The 1996 practice guideline of the Dutch College of General Practitioners (NHG) on vaginal discharge has been updated. Most women who visit their doctor with complaints about vaginal discharge do not have an increased risk of a sexually-transmitted disease. Investigations into vaginal discharge comprise history taking, physical examination and microscopic analysis in the laboratory of the general practitioner. Additional investigation into Chlamydia, gonorrhoea and Trichomonas infection is only necessary if the patient history reveals an increased risk of a sexually-transmitted disease. A Candida infection or bacterial vaginosis should only be treated if the patient experiences bothersome complaints. Treatment of a Candida infection consists of a vaginally applied imidazole compound. Bacterial vaginosis can be treated with oral administration of metronidazole. Patients with vaginal fluor can be examined and, if necessary, treated by their general practitioner. Referral to a gynaecologist is rarely necessary.

[Summary of the practice guideline 'Pelvic inflammatory disease' (first revision) from the Dutch College of General Practitioners]

The 1995 guideline on pelvic inflammatory disease (PID) has been updated. The general practitioner should consider PID whenever a woman of childbearing age complains of lower abdominal pain; the diagnosis should then be based on 5 criteria: (a) non-acute lower abdominal pain; (b) pain on upward movement or adnexal tenderness during vaginal touch; (c) painful or swollen adnexae; (d) ESR > or = 15 mm in the 1st hour or a temperature > 38 degree C, and (e) no indications for other diseases, such as appendicitis or an extra-uterine pregnancy. In case of diagnostic doubt, a gynaecologist must be consulted. Rapid treatment with antibiotics diminishes symptoms, shortens the course of disease, and may prevent complications such as infertility or extra-uterine pregnancy. Treatment should be started with ofloxacin and metronidazole. Due to the increasing antibiotic resistance of Neisseria gonorrhoeae, when there are indications for this pathogen the medicinal treatment should immediately be directed at it by means of cefotaxim, doxycycline and metronidazole. In his or her information to the patient, the general practitioner should devote attention to the major role of sexually transmissible micro-organisms and give advice, if necessary, regarding high-risk behaviour.

[The Dutch Health Council report on screening for Chlamydia: too reserved]

The prevalence of sexually transmitted diseases (STDs) increased in the Netherlands in the years 2000-2003. A recent population-based study showed that Chlamydia infections were a problem in urbanised areas; prevalence in rural areas was low. In 2004, the Dutch Health Council advised against a national screening programme for Chlamydia. However, the newest figures on the distribution of Chlamydia infections suggest that screening in large cities might be cost-effective. Much can be learned from the screening programme in the United Kingdom.

Effect of triamcinolone acetonide injections on hemiplegic shoulder pain : A randomized clinical trial

Background and Purpose-Hemiplegic shoulder pain is not uncommon after stroke. Its origin is still unknown, and although many different methods of treatment are applied, none have yet been proved to be effective. We sought to study the efficacy of 3 injections of intra-articular triamcinolone acetonide on pain and arm function in stroke patients with hemiplegic shoulder pain.

METHODS

-In a multicenter, randomized, placebo-controlled clinical trial, patients with hemiplegic shoulder pain received either 3 intra-articular injections of 40 mg triamcinolone acetonide or 1 mL physiological saline solution (placebo). Primary outcomes were pain measured according to 3 visual analogue scales (score range, 0 to 10), and arm function was measured by means of the Action Research Arm test and the Fugl-Meyer assessment scale; secondary outcomes were passive external rotation of the shoulder and general functioning measured according to Barthel Index and the Rehabilitation Activities Profile.

RESULTS

-In the triamcinolone group (n=18), the median decrease in pain, 3 weeks after the last injection, was 2.3 (interquartile range, 0.3 to 4.3) versus 0.2 (interquartile range, -0.5 to 2.2) in the placebo group. This result was not statistically significant. The change in the other outcome measures did not differ significantly between the 2 treatment groups. Twenty-five patients reported side effects.

CONCLUSIONS

-In the 37 participants included in this study, triamcinolone injections seemed to decrease hemiplegic shoulder pain and to accelerate recovery, but this effect was not statistically significant. Therefore, on the basis of the results of this study, these injections cannot be recommended for the treatment of patients with hemiplegic shoulder pain.

'Numbness of the feet' is a poor indicator for polyneuropathy in Type 2 diabetic patients

AIMS

To identify neuropathic sensory symptoms associated with a clinical neurological examination (CNE) and to investigate whether these symptoms could be used as a diagnostic or screening tool for diabetic polyneuropathy in general practice.

METHODS

Five hundred and eighty-eight patients with Type 2 diabetes, recruited from 26 general practices in the Netherlands, underwent a CNE and completed a diabetes symptom checklist that included 10 items on neuropathic sensory symptoms. Linear regression analyses were performed to assess the association between neuropathic symptoms and CNE. Receiver operating characteristic (ROC) curves were created to assess the diagnostic properties of neuropathic symptoms.

RESULTS

In this population, with a mean age of 66.8 years, 32% were identified with diabetic polyneuropathy according to the CNE. Variables that showed the strongest association with CNE score were age (beta = 0.41), symptoms of sensory alteration (beta = 0.27), and the item 'numbness of the feet' (beta = 0.35) in particular. ROC curves showed that prediction of diabetic polyneuropathy from these symptoms was unsatisfying. The sensitivity and specificity of daily symptoms of 'numbness of the feet' were 28% and 93%, respectively, in patients <68 years, and 22% and 92%, respectively, in patients > or =68 years.

CONCLUSIONS

Identification of neuropathic sensory symptoms is not useful as a diagnostic or even a screening tool in the assessment of diabetic neuropathy in daily practice. Therefore, the results reported in this paper mandate an annual foot examination by the general practitioner.

Metabolic control and morbidity of type 2 diabetic patients in a general practice network

METHODS

Glycaemic control and the prevalence of modifiable cardiovascular risk factors, and micro- and macrovascular morbidity was examined in 637 Type 2 diabetic patients in general practice, of whom 405 consented to undergo a more extensive examination.

RESULTS

In these 405 patients, HbA1c was > or = 7% in 56.6%, and hypertension and dyslipidaemia were found in 59.8% and 46.5% of the patients, respectively. The level of cardiovascular risk factors was acceptable, according to the European guidelines, in the following proportions of patients: BMI 45.0%; total cholesterol 69.1%; HDL-cholesterol 68.1%; triglycerides 67.8%; current blood pressure 89.8%; and smoking 21.0%. Retinopathy was present in 12.5% and microalbuminuria in 27.0% of the patients. In all 637 patients, the prevalence of angina pectoris was 17.7%, of myocardial infarction 11.4% and of congestive heart failure 10.7%.

CONCLUSION

The care for Type 2 diabetic patients needs improvement and should focus on cardiovascular risk factors as much as on glycaemic control.

How valid is fasting plasma glucose as a parameter of glycemic control in non-insulin-using patients with type 2 diabetes?

OBJECTIVE

To assess the value of fasting blood glucose as a parameter for glycemic control in type 2 diabetic patients not using insulin.

RESEARCH DESIGN AND METHODS

In 1,020 type 2 diabetic patients treated with diet or oral hypoglycemic agents (OHAs), measurements of fasting plasma glucose (FPG) and HbA1c were taken. In 617 patients, the measurement could be repeated after 3 months. Cross-sectional correlation coefficients were calculated for the association between HbA1c and FPG. Receiver-operating characteristic (ROC)-curve analyses were applied to examine the performance of FPG as a diagnostic test for HbA1c. Longitudinally, the change in FPG was compared with the change in HbA1c, with both correlation measures and ROC curve analyses.

RESULTS

Correlation coefficients between HbA1c and FPG and between FPG change and HbA1c change were 0.77 and 0.65, respectively. ROC curve analysis showed that HbA1c is difficult to predict from FPG values: 66% of the patients with good HbA1c (< 7.0%) were identified as such by FPG values < 7.8 mmol/l. As a test for HbA1c change, FPG change performed moderately: the highest combined values of sensitivity and specificity (87.7 and 57%, respectively) were reached at a cutoff point of zero in the range of FPG change values.

CONCLUSIONS

FPG and HbA1c values that do not correspond are not rare in type 2 diabetic patients on diet or OHA treatment. HbA1c is difficult to predict from FPG values, and even more difficult is the prediction of HbA1c changes from FPG changes.

[Systematic home screening for Chlamydia trachomatis infections of asymptomatic men and women in family practice by means of mail-in urine samples]

OBJECTIVE

To determine the prevalence and determinants of Chlamydia trachomatis (CT) infections among asymptomatic men and women in general practice. To determine participation rates in a systematic screening programme in general practice, using home obtained mailed urine samples.

DESIGN

Cross-sectional study.

METHODS

In 15 general practices in Amsterdam, the Netherlands, a sample of 11,005 persons (5541 women and 5464 men), aged 15-40 were invited to send in a urine sample and a completed questionnaire by mail. The urine samples were tested using the ligase chain reaction for DNA amplification. Patients diagnosed with CT were treated and partner notification was performed.

RESULTS

33% of invited males (1809/5464) and 50% of females (2751/5541) sent in the study material. Older patients participated more frequently than younger patients. Participation rates among persons with a Dutch background were higher than rates among persons from other ethnic groups. In 42 men and 79 women a CT infection was identified (2.3% and 2.9% respectively). Infections were more prevalent in patients from Surinam and the Dutch Antilles and in the age category 21-25 years. Type of health insurance as a proxy measure of socioeconomic status was not an indicator of infection.

CONCLUSION

The participation in this systematic screening using mail-sent urine samples was 33% in men and 50% in women. The CT prevalences among asymptomatic men and women were 2.3% and 2.9% respectively.

The painful hemiplegic shoulder: effects of intra-articular triamcinolone acetonide

Effects of intra-articular triamcinolone acetonide on pain and passive range of motion (ROM) in the painful hemiplegic shoulder were studied. A Multiple baseline (or AB) design across seven subjects was used. The length of the baseline condition (or A phase) was either 2 or 3 wk, and randomized across subjects. Subsequently, a treatment condition (or B phase) of 4 wk was applied during which three intra-articular injections of triamcinolone acetonide were administered at day 1, 8, and 22. Pain and ROM were the primary outcome parameters and were measured three times each week by means of a visual analogue scale (VAS) and a fluid-filled goniometer, respectively. In addition, a number of secondary outcome parameters were assessed, i.e., spastic muscle activity (Ashworth scale), motor function (Fugl-Meyer index), upper limb function (action research arm test) and signs and symptoms of a shoulder hand syndrome (clinical scoring list). Statistical analysis of the combined time series showed significant effects on pain (P = 0.025). Analysis of the individual time series revealed that five out of seven patients had significant reduction of pain. ROM improved significantly in four out of seven patients. However, improvement of ROM did not reach significance at the group level (P = 0.13). None of the secondary parameters showed significant changes. The correlation coefficient between upper limb function (ARA) at intake and size of treatment effect approached a level of significance (P = 0.09). The results indicate that intra-articular triamcinolone may be of benefit in reducing hemiplegic shoulder pain.

Effect of lactic acid suppositories compared with oral metronidazole and placebo in bacterial vaginosis: a randomised clinical trial

OBJECTIVE

To compare the effect of lactic acid locally, metronidazole orally and placebo in women with bacterial vaginosis.

DESIGN

Randomised clinical trial.

SETTING

30 general practices in the Netherlands.

PATIENTS

125 women consulting the general practitioner for symptomatic bacterial vaginosis.

MAIN OUTCOME MEASURES

Duration of subjective symptoms, recurrence of symptoms, clinically diagnosed cure, adverse events.

RESULTS

Survival analysis showed a significantly faster disappearance of symptoms in the metronidazole category compared with both lactic acid and placebo (p = 0.0005 metronidazole v placebo, p = 0.0002 metronidazole v lactic acid p = 0.6521 lactic acid v placebo [The stratified Mantel Cox test]). The median duration until absence of symptoms was 21 days for metronidazole and 80 days for placebo. Disappearance of symptoms did not occur in 50% of the lactic acid group in 90 days. Recurrence rates of symptoms were similar over the treatment categories (p = 0.13 metronidazole v placebo and p = 0.12 lactic acid v placebo). After 2 weeks cure rates (cure defined as less than three of four clinical criteria present) were 83%, 49% and 47% for metronidazole, lactic acid and placebo category respectively. At that time cure rates (cure defined as none of three clinical criteria present) were 10%, 0% and 3%. After four weeks and three months these figures were: 55%, 20%, 20% and 64%, 28%, 28%. No differences in adverse events were found between the three interventions.

CONCLUSIONS

Lactic acid suppositories are ineffective, metronidazole capsules are effective on signs and symptoms in bacterial vaginosis. A considerable proportion of the patients recover without active medication.

Vaginal symptoms of unknown aetiology: a study in Dutch general practice

Vaginal symptoms are frequently presented by women to general practitioners. In many cases, the aetiology of these symptoms remains unknown. This study focused on the factors associated with microbiologically unexplained vaginal symptoms, the course of symptoms and signs in these cases, and factors modifying this course. In a group of 610 women presenting to their general practitioner with vaginal symptoms (itching, irritation, abnormal but non-bloody discharge) the distribution of diagnoses was studied and factors associated with symptoms of unknown aetiology were identified using logistic regression analysis. During a three month follow up, the course of symptoms and signs was studied in 139 women with unexplained vaginal symptoms, using survival analysis methods. It was found that 25% of all the women had symptoms of unknown aetiology. A larger number of these women, compared with women with other diagnoses, were Caucasian, married, more highly educated, used oral contraceptives and reported psychological distress. During the follow-up period, a specific infection was diagnosed in less than 20% of the women with unexplained vaginal symptoms. Over half of the women (54%) recovered within three months. Short duration of symptoms before presentation was associated with a higher probability of recovery. From the study, it was found that many women visiting the general practitioner for vaginal symptoms had no demonstrable microbial disorder. Often these symptoms were transient and disappeared without intervention. Persistent symptoms may call for further examination where somatic, as well as psychosocial, factors should be taken into account.

A comparison of yield from cervix versus vagina for culturing Candida albicans and Trichomonas vaginalis

OBJECTIVE

To determine the agreement of culture results of Candida albicans and Trichomonas vaginalis from the cervix versus posterior fornix in women with vaginal symptoms.

DESIGN

Same patient comparison of culture results from two sample sites.

SETTING

Twenty one general practices in Amsterdam and the east of the Netherlands.

SUBJECTS

Six hundred and eighty two women aged 15 to 55 years with vaginal symptoms, seen between 1 October 1987 and 31 May 1990.

MAIN OUTCOME MEASURES

For each site (cervix and posterior fornix) the proportion of detected C albicans and T vaginalis. The sensitivity of the cervical swab related to the vaginal one. The percentage of concordance for both microorganisms.

RESULTS

In 248 (34%) women C albicans was diagnosed and in 38 (6%) T vaginalis. In 99% of the proven C albicans cases, the yeast was found in the vagina. In 94% C albicans was isolated from the cervix. Sensitivity of the cervical swab was 94%. In 98% of the patients a concordant observation was made regarding detection of yeast. In 97% of the proven T vaginalis cases the protozoon was found in the vagina. In 91% T vaginalis was detected from the cervical swab. Sensitivity of the cervical swab was 92%. The culture results were concordant in 99%.

CONCLUSION

The yield from the vaginal source was slightly better than that from the cervix for culture of both microorganisms. For screening purposes, specimen-collection for culture of N gonorrhoeae, C albicans and T vaginalis can be combined in one swab taken from the cervix.

Pleiotropy in Triazine-Resistant Brassica napus: Ontogenetic and Diurnal Influences on Photosynthesis

Studies were conducted that supported the hypothesis that the mutation to the psbA plastid gene that confers S-triazine resistance (R) in Brassica napus also results in an altered diurnal pattern of photosynthetic carbon assimilation (A) relative to that of the susceptible (S) wild type, and that these patterns change over the ontogeny of a plant. Photosynthetic photon flux density, under closely controlled environmental conditions, was incrementally increased and decreased on either side of the midday maxima of 1150 to 1300 mumol quanta m(-2) s(-1). In all experiments, A approximately tracked the increasing and decreasing diurnal light levels. Younger (3- to 4-leaf) R plants had greater photosynthetic rates early and late in the diurnal light period, whereas those of S plants were greater during midday as well as during the photoperiod as a whole. These relative photosynthetic characteristics of R and S plants changed in several ways with ontogeny. As the plants aged during the vegetative phase of development, S plants gradually assimilated more carbon in the early, and then in the late, part of the day. At the end of the vegetative phase of development, R plant carbon assimilation was less relative to S plants at most times of the day, and was never greater. This relationship between the two biotypes dramatically changed with the onset of the reproductive phase (8(1/2) to 9(1/2) leaf) of plant development: R plants assimilated more carbon than S plants during all periods of the diurnal light period with the exception of the late part of the day. In addition to these differences in A, R plant stomatal function differed from that in S plants. R plant leaves were always cooler than S plant leaves under the same environmental and diurnal conditions. Correlated with this difference in leaf temperature were equal or greater total conductances to water vapor and intercellular CO(2) partial pressures in R compared to S leaves in most instances. These studies indicate a more complex pattern of photosynthetic carbon assimilation than previously observed. The photosynthetic superiority of one biotype relative to the other was a function of the time of day and the age of the plant. These studies also suggest that R plants may have an adaptive advantage over S plants in certain unfavorable ecological niches independent of the presence of S-triazine herbicides, such as cool, low-light environments early and late in the day, as well as late in the plants' development. This advantage could result in R biotypes appearing in populations of a species in greater numbers than plastidic mutation alone could cause.

Regulation of Photosynthesis in Triazine-Resistant and -Susceptible Brassica napus

The response of photosynthetic carbon assimilation and chlorophyll fluorescence quenching to changes in intercellular CO(2) partial pressure (C(i)), O(2) partial pressure, and leaf temperature (15-35 degrees C) in triazine-resistant and -susceptible biotypes of Brassica napus were examined to determine the effects of the changes in the resistant biotype on the overall process of photosynthesis in intact leaves. Three categories of photosynthetic regulation were observed. The first category of photosynthetic response, ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco)-limited photosynthesis, was observed at 15, 25, and 35 degrees C leaf temperatures with low C(i). When the carbon assimilation rate was Rubisco-limited, there was little difference between the resistant and susceptible biotypes, and Rubisco activity parameters were similar between the two biotypes. A second category, called feedback-limited photosynthesis, was evident at 15 and 25 degrees C above 300 microbars C(i). The third category, photosynthetic electron transport-limited photosynthesis, was evident at 25 and 35 degrees C at moderate to high CO(2). At low temperature, when the response curves of carbon assimilation to C(i) indicated little or no electron transport limitation, the carbon assimilation rate was similar in the resistant and susceptible biotypes. With increasing temperature, more electron transport-limited carbon assimilation was observed, and a greater difference between resistant and susceptible biotypes was observed. These observations reveal the increasing importance of photosynthetic electron transport in controlling the overall rate of photosynthesis in the resistant biotype as temperature increases. Photochemical quenching of chlorophyll fluorescence (q(P)) in the resistant biotype never exceeded 60%, and triazine resistance effects were more evident when the susceptible biotype had greater than 60% q(P), but not when it had less than 60% q(P).