Association between prescribing of cardiovascular and psychotropic medications and hospital admission for falls or fractures

BACKGROUND AND OBJECTIVE

Falls are a major cause of morbidity and mortality in the elderly. This study examined the frequency of hospital admission for falls or fractures, and the association with a recent change in the use of cardiovascular and psychotropic medications.

METHODS

We conducted a retrospective case-cohort study of 39,813 patients aged >65 years from 40 Scottish general practices. Data on current prescriptions, dates of drug changes (defined as increases in dose or starting new drugs), diagnoses and clinical measurements were extracted from primary care electronic records, linked to national hospital admissions data. Multivariable logistic regression was used to model the association of change in prescribing of cardiovascular or psychotropic medication with admission to hospital for falls or fractures in the following 60 days.

RESULTS

A total of 838 patients (2.1 %) were admitted in the 1-year study period. Following adjustment for factors including age, sex, socioeconomic deprivation, co-morbidity and current prescribing, changes in both cardiovascular and psychotropic medications were associated with subsequent admission for falls or fractures (odds ratio [OR] 1.54 [95 % confidence interval (CI) 1.17-2.03] and 1.68 [95 % CI 1.28-2.22], respectively). There was no evidence for a difference in the effect of change in medication for different cardiovascular drug types (p = 0.86), but there was evidence (p = 0.003) for variation in the association between change in different psychotropic medications and admission; the strongest associations were observed for changes in selective serotonin reuptake inhibitor (SSRI) antidepressants (OR 1.99 [95 % CI 1.29-3.08]), non-SSRI/tricyclic antidepressants (OR 4.39 [95 % CI 2.21-8.71]) and combination psychotropic medication (OR 3.05 [95 % CI 1.66-5.63]).

CONCLUSIONS

Recent changes in psychotropic and cardiovascular medications are associated with a substantial increase in risk of hospital admission for falls and fractures. Caution should thus be taken when instigating prescribing changes in relation to these medicines, particularly in individuals already considered to be at high risk, such as those with multiple co-morbidities and the oldest old.

ACE inhibitor and angiotensin receptor-II antagonist prescribing and hospital admissions with acute kidney injury: a longitudinal ecological study

Background

ACE Inhibitors (ACE-I) and Angiotensin-Receptor Antagonists (ARAs) are commonly prescribed but can cause acute kidney injury (AKI) during intercurrent illness. Rates of hospitalization with AKI are increasing. We aimed to determine whether hospital AKI admission rates are associated with increased ACE-I/ARA prescribing.

Methods and Findings

English NHS prescribing data for ACE-I/ARA prescriptions were matched at the level of the general practice to numbers of hospital admissions with a primary diagnosis of AKI. Numbers of prescriptions were weighted for the demographic characteristics of general practices by expressing prescribing as rates where the denominator is Age, Sex, and Temporary Resident Originated Prescribing Units (ASTRO-PUs). We performed a mixed-effect Poisson regression to model the number of admissions for AKI occurring in each practice for each of 4 years from 1/4/2007.

From 2007/8-2010/11, crude AKI admission rates increased from 0.38 to 0.57 per 1000 patients (51.6% increase), and national annual ACE-I/ARA prescribing rates increased by 0.032 from 0.202 to 0.234 (15.8% increase). There was strong evidence (p<0.001) that increases in practice-level prescribing of ACE-I/ARA over the study period were associated with an increase in AKI admission rates. The increase in prescribing seen in a typical practice corresponded to an increase in admissions of approximately 5.1% (rate ratio = 1.051 for a 0.03 per ASTRO-PU increase in annual prescribing rate, 95%CI 1.047-1.055). Using the regression model we predict that 1,636 (95%CI 1,540-1,780) AKI admissions would have been avoided if prescribing rates were at the 2007/8 level, equivalent to 14.8% of the total increase in AKI admissions.

Conclusion

In this ecological analysis, up to 15% of the increase in AKI admissions in England over a 4-year time period is potentially attributable to increased prescribing of ACE-I and ARAs. However, these findings are limited by the lack of patient level data such as indication for prescribing and patient characteristics.

The accuracy of diagnostic coding for acute kidney injury in England - a single centre study

BACKGROUND

Acute kidney injury (AKI) is an independent risk factor for mortality and is responsible for a significant burden of healthcare expenditure, so accurate measurement of its incidence is important. Administrative coding data has been used for assessing AKI incidence, and shows an increasing proportion of hospital bed days attributable to AKI. However, the accuracy of coding for AKI and changes in coding over time have not been studied in England.

METHODS

We studied a random sample of admissions from 2005 and 2010 where ICD-10 code N17 (acute renal failure) was recorded in the administrative coding data at one acute NHS Foundation Trust in England. Using the medical notes and computerised records we examined the demographic and clinical details of these admissions.

RESULTS

Against a 6.3% (95% CI 4.8-7.9%) increase in all non-elective admissions, we found a 64% increase in acute renal failure admissions (95% CI 41%-92%, p < 0.001) in 2010 compared to 2005. Median age was 78 years (IQR 72-87), 11-25% had a relevant pre-admission co-morbidity and 64% (55-73%) were taking drugs known to be associated with AKI. Over both years, 95% (91-99%) of cases examined met the Kidney Disease: Improving Global Outcomes criteria for AKI.

CONCLUSIONS

Patients with hospital admissions where AKI has been coded are elderly with multiple co-morbidities. Our results demonstrate a high positive predictive value of coding data for a clinical diagnosis of AKI, with no suggestion of marked changes in coding of AKI between 2005 and 2010.

The effect of physical multimorbidity, mental health conditions and socioeconomic deprivation on unplanned admissions to hospital: a retrospective cohort study

BACKGROUND

Multimorbidity, the presence of more than 1 long-term disorder, is associated with increased use of health services, but unplanned admissions to hospital may often be undesirable. Furthermore, socioeconomic deprivation and mental health comorbidity may lead to additional unplanned admissions. We examined the association between unplanned admission to hospital and physical multimorbidity, mental health and socioeconomic deprivation.

METHODS

We conducted a retrospective cohort study using data from 180 815 patients aged 20 years and older who were registered with 40 general practices in Scotland. Details of 32 physical and 8 mental health morbidities were extracted from the patients' electronic health records (as of Apr. 1, 2006) and linked to hospital admission data. We then recorded the occurrence of unplanned or potentially preventable unplanned acute (nonpsychiatric) admissions to hospital in the subsequent 12 months. We used logistic regression models, adjusting for age and sex, to determine associations between unplanned or potentially preventable unplanned admissions to hospital and physical multimorbidity, mental health and socioeconomic deprivation.

RESULTS

We identified 10 828 (6.0%) patients who had at least 1 unplanned admission to hospital and 2037 (1.1%) patients who had at least 1 potentially preventable unplanned admission to hospital. Both unplanned and potentially preventable unplanned admissions were independently associated with increasing physical multimorbidity (for ≥4 v. 0 conditions, odds ratio [OR] 5.87 [95% confidence interval (CI) 5.45-6.32] for unplanned admissions, OR 14.38 [95% CI 11.87-17.43] for potentially preventable unplanned admissions), mental health conditions (for ≥1 v. 0 conditions, OR 2.01 [95% CI 1.92-2.09] for unplanned admissions, OR 1.80 [95% CI 1.64-1.97] for potentially preventable unplanned admissions) and socioeconomic deprivation (for most v. least deprived quintile, OR 1.56 [95% CI 1.43-1.70] for unplanned admissions, OR 1.98 [95% CI 1.63-2.41] for potentially preventable unplanned admissions).

INTERPRETATION

Physical multimorbidity was strongly associated with unplanned admission to hospital, including admissions that were potentially preventable. The risk of admission to hospital was exacerbated by the coexistence of mental health conditions and socioeconomic deprivation.

Cardiovascular risk

Cardiovascular disease is a major, growing, worldwide problem. It is important that individuals at risk of developing cardiovascular disease can be effectively identified and appropriately stratified according to risk. This review examines what we understand by the term risk, traditional and novel risk factors, clinical scoring systems, and the use of risk for informing prescribing decisions. Many different cardiovascular risk factors have been identified. Established, traditional factors such as ageing are powerful predictors of adverse outcome, and in the case of hypertension and dyslipidaemia are the major targets for therapeutic intervention. Numerous novel biomarkers have also been described, such as inflammatory and genetic markers. These have yet to be shown to be of value in improving risk prediction, but may represent potential therapeutic targets and facilitate more targeted use of existing therapies. Risk factors have been incorporated into several cardiovascular disease prediction algorithms, such as the Framingham equation, SCORE and QRISK. These have relatively poor predictive power, and uncertainties remain with regards to aspects such as choice of equation, different risk thresholds and the roles of relative risk, lifetime risk and reversible factors in identifying and treating at-risk individuals. Nonetheless, such scores provide objective and transparent means of quantifying risk and their integration into therapeutic guidelines enables equitable and cost-effective distribution of health service resources and improves the consistency and quality of clinical decision making.

A retrospective cohort study assessing patient characteristics and the incidence of cardiovascular disease using linked routine primary and secondary care data

OBJECTIVES

Data linkage combines information from several clinical data sets. The authors examined whether coding inconsistencies for cardiovascular disease between components of linked data sets result in differences in apparent population characteristics.

DESIGN

Retrospective cohort study.

SETTING

Routine primary care data from 40 Scottish general practitioner (GP) surgeries linked to national hospital records.

PARTICIPANTS

240 846 patients, aged 20 years or older, registered at a GP surgery.

OUTCOMES

Cases of myocardial infarction, ischaemic heart disease and stroke (cerebrovascular disease) were identified from GP and hospital records. Patient characteristics and incidence rates were assessed for all three clinical outcomes, based on GP, hospital, paired GP/hospital (similar diagnoses recorded simultaneously in both data sets) or pooled GP/hospital records (diagnosis recorded in either or both data sets).

RESULTS

For all three outcomes, the authors found evidence (p<0.05) of different characteristics when using different methods of case identification. Prescribing of cardiovascular medicines for ischaemic heart disease was greatest for cases identified using paired records (p≤0.013). For all conditions, 30-day case fatality rates were higher for cases identified using hospital compared with GP or paired data, most noticeably for myocardial infarction (hospital 20%, GP 4%, p=0.001). Incidence rates were highest using pooled GP/hospital data and lowest using paired data.

CONCLUSIONS

Differences exist in patient characteristics and disease incidence for cardiovascular conditions, depending on the data source. This has implications for studies using routine clinical data.

Renal Dysfunction Does Not Affect the Peripheral-to-Central Arterial Pressure Transfer Function

Arterial generalized transfer functions (GTFs) are increasingly used to estimate central pressure from peripheral measurements. Analysis of derived central waveforms may be valuable in the assessment of patients with chronic kidney disease. The aim of this study was to assess whether the GTF is affected by renal disease. Ninety-four subjects with varying degrees of renal function (Kidney Disease Outcomes Quality Initiative stages 1 to 5; 14 controls) had simultaneous measurements of carotid and radial waveforms made by applanation tonometry. GTFs were calculated by Fourier analysis for each subject group. Derived carotid waveforms were obtained by applying an independently generated GTF to the radial waveform. Glomerular filtration rate inversely correlated with central systolic ( R =−0.42; P <0.001), mean ( R =−0.34; P <0.01) and diastolic ( R =−-0.27, P <0.01) blood pressures, as well as central augmentation index ( R =−0.30; P <0.01) and carotid-femoral pulse wave velocity ( R =−0.33; P <0.001). Derived waveforms were not significantly different from measured waveforms in terms of systolic blood pressure, augmentation index, maximum slope, or the delay between the incident and reflected waves, although the derived waveforms slightly underestimated the systolic ejection period (−4.4±0.9 ms; P <0.001). Overall root-mean-square error was 2.4±0.1 mm Hg. No significant relationship existed between the degree of bias of any derived waveform measure and glomerular filtration rate or chronic kidney disease stage ( P >0.16). No significant differences between chronic kidney disease stages were observed in transfer function gain or phase ( P >0.05). We conclude that the peripheral-to-central GTF is not affected by degree of renal dysfunction and can be used with equivalence in patients with varying degrees of chronic kidney disease.

Deprivation-based risk scores: the re-emergence of postcode prescribing in the UK?

BACKGROUND/OBJECTIVES

Socioeconomic gradients exist in the prevalence of cardiovascular disease. This has prompted the development of risk scores such as ASSIGN and QRISK, which incorporate measures of deprivation, to address the issue of underprescribing of primary preventive medicines in the socially disadvantaged. The scores use area-based measures of deprivation rather than the socioeconomic status of the individual. We examined to what extent the decision to treat a patient might be influenced by where that individual lived.

METHODS

On the basis of individual patient risk factor data from the Scottish Health Survey, we compared the theoretical level of deprivation [Scottish Index of Multiple Deprivation (SIMD)] required to give a person an ASSIGN risk of 20% (the treatment cut-off), with the person's actual SIMD quintile. We assumed that patients are more likely to move between areas of similar deprivation (i.e. the same SIMD quintile). If the theoretical SIMD value for that individual fell within their actual SIMD quintile, we assumed that prescribing decisions could be influenced by the area of residence.

RESULTS

If the ASSIGN risk score was implemented, the area of residence would affect the decision to initiate statins in the case of 15.7% of the population (aged 30-74 years), and for borderline hypertension, in 3.0%. This corresponds to 407 000 and 15 000 people, respectively, in Scotland and 4.6 million and 169 000 in the entire UK.

CONCLUSION

These findings demonstrate that by using cardiovascular risk scores based on area deprivation, primary prevention treatment decisions will be affected by the area of residence in a large number of individuals.

Similarity between the suprasystolic wideband external pulse wave and the first derivative of the intra-arterial pulse wave

BACKGROUND

Wideband external pulse (WEP) monitoring, using a broad bandwidth piezoelectric sensor located over the brachial artery under the distal edge of a sphygmomanometer cuff, can be used for evaluating the contour of the arterial pressure pulse wave. The pulse contour contains valuable information relating to cardiovascular function which may be of clinical use in addition to blood pressure measurements. The aim of this study was to compare the shape of the WEP signal during inflation of the cuff to suprasystolic pressure, with intra-arterial pressure waves, after the administration of vasoactive drugs.

METHODS

Radial intra-arterial and suprasystolic WEP waveforms were recorded in 11 healthy men (mean 23 yr) before and at the end of infusion of glyceryl trinitrate, angiotensin II, norepinephrine, and salbutamol. Waveform similarity was assessed by comparing the timing and pressure of incident and reflected waves and by root mean square error (RMSE).

RESULTS

The WEP signal was found to closely resemble the first derivative of intra-arterial pressure. The WEP signal could be used to derive an arterial pressure wave with minimal bias in the timing of incident [- 8 (18) ms, mean (SD)] and reflected [- 1 (24) ms] waves. Augmentation index was underestimated by WEP [- 7 (18)%]. WEP also provided a measure of compliance which correlated with pulse wave velocity (r = - 0.44). RMSE values after the administration of each of the four drugs mentioned earlier were 12.4 (3.8), 17.7 (5.0), 22.1 (11.7), and 28.9 (22.4) mm Hg, respectively. Changes in derived WEP signals were similar to those measured by arterial line with all drugs.

CONCLUSIONS

The suprasystolic WEP signals can be used to derive arterial pressure waves which, although not identical, track changes in the intra-arterial pulse wave induced by vasoactive drugs.

Selectivity of NSAIDs for COX-2 and cardiovascular outcome

BACKGROUND

Nonsteroidal anti-inflammatory drugs (NSAIDs) with increased selectivity for the cyclooxygenase-2 (COX-2) isoform reduce gastrotoxicity but may increase adverse cardiovascular events.

METHODS

We searched the literature for studies that reported the odds ratio (OR) for such events following exposure to NSAIDs.

RESULTS

For studies comparing NSAID use with no use, increased COX-2 selectivity was significantly related to cardiovascular risk (log OR) amongst observational studies (R = -0.34, P < 0.001) and randomized controlled trials (RCTs) (R = -0.56, P < 0.001). For studies comparing NSAIDs, difference in selectivity was related to risk for observational studies (R = -0.28, P = 0.005) but not for RCTs (R = -0.23, P = 0.15).

CONCLUSIONS

Although increased COX-2 selectivity may reduce gastrotoxicity, this may be at the cost of increasing cardiovascular risk.

Pulse transit time measured from the ECG: an unreliable marker of beat-to-beat blood pressure

The arterial pulse-wave transit time can be measured between the ECG R-wave and the finger pulse (rPTT), and has been shown previously to have a linear correlation with blood pressure (BP). We hypothesized that the relationship between rPTT, preejection period (PEP; the R-wave/mechanical cardiac delay), and BP would vary with different vasoactive drugs. Twelve healthy men (mean age 22 yr) were studied. Beat-to-beat measurements were made of rPTT (using ECG and photoplethysmograph finger probe), intra-arterial radial pressure, PEP (using cardiac bioimpedance), and transit time minus PEP (pPTT). Four drugs (glyceryl trinitrate, angiotensin II, norepinephrine, salbutamol) were administered intravenously over 15 min, with stepped dosage increase every 5 min and a 25-min saline washout between agents. All subjects in all conditions had a negative linear correlation (R2 = 0.39) between rPTT and systolic BP (SBP), generally constant between different drugs, apart from four subjects who had a positive rPTT/SBP correlation with salbutamol. The 95% limits of agreement between measured and rPTT-predicted SBP were +/-17.0 mmHg. Beat-to-beat variability of rPTT showed better coherence with SBP variability than it did with heart rate variability (P < 0.001). PEP accounted for a substantial and variable proportion of rPTT (12-35%). Diastolic (DBP) and mean arterial BP (MAP) correlated poorly with rPTT (R2 = 0.02 and 0.08, respectively) but better with pPTT (rPTT corrected for PEP, R2 = 0.41 and 0.45, respectively). The 95% limits of agreement between measured and pPTT-predicted DBP were +/- 17.3 mmHg. In conclusion, the negative correlation between rPTT and SBP is generally constant, even with marked hemodynamic perturbations. However, the relationship is not reliable enough for rPTT to be used as a surrogate marker of SBP, although it may be useful in assessing BP variability. DBP and MAP cannot be predicted from rPTT without correction for PEP. The significant contribution of PEP to rPTT means that rPTT should not be used as a marker of purely vascular function.

The prevalence of toxoplasma antibodies in pregnant Nigerian women and the occurrence of stillbirth and congenital malformation

Toxoplasma antibody serological tests were carried out using the Dye test on sera of pregnant and postpartum Nigerian women to investigate whether there was any association between the levels of antibody titres and the occurrence of stillbirths and congenital malformations. There was a high prevalence of toxoplasma antibodies in the sera of both pregnant and postpartum women. The prevalence rates for the pregnant women ranged from 72.5% to 88.8% with an overall rate of 75.4%; whilst for the postpartum women, the prevalence rates ranged from 75.0% to 94.4% with an overall rate of 80.5%. The toxoplasma antibody titres of the sera from the live-born babies as well as stillbirths and congenitally malformed babies ranged from 1:16 to 1:1024. The exact role played by toxoplasma in the occurrence of stillbirths and congenital malformation in our area of study is, however, not clear. For future research, it is suggested that larger samples be studied in order to enhance the validity of the findings of the present study.

The prevalence of Toxoplasma infection among pregnant women in Ibadan, Nigeria

The seroprevalence of toxoplasmosis in pregnant women from the inner area of Ibadan was determined by the dye test. Two hundred and seventy-three of the 352 women (78%) had dye test titres of 1/16 or greater with 165 (47%) having titres of 1/128 or greater. In contrast, 42 of 192 pregnant women (22%) from the Swansea area of the UK were dye test positive with only six (3%) having titres of 1/128. The possibility that reinfection or recrudescence is responsible for maintaining high antibody levels in African women and the consequence of this high level of infection in relation to potential human immune deficiency virus (HIV) infections are discussed. Social and environmental conditions indicate that the source of infection is contact with cat faeces.

Potential role of IgG avidity for diagnosing toxoplasmosis

Sera from 20 cases of toxoplasmic lymphadenopathy were examined by an enzyme linked immunosorbent assay toxoplasma IgG avidity (ELISA) at two laboratories. The results obtained were largely in agreement and showed that sera from patients with acute infection had low avidity IgG (30% or less), whereas sera from patients with chronic infection had high avidity IgG (40% or more). It is suggested that this type of assay could have a useful complementary role in antenatal testing for toxoplasmosis.

Gastric cancer: a continuing diagnostic challenge--a district general hospital's experience

We present the results of 87 consecutively referred patients with malignant gastric tumours who presented to the North Middlesex Hospital between 1980 and 1984, inclusively. The results of this prospective study showed a high incidence of adenocarcinoma situated in the cardia (16 per cent of patients), and antral carcinomas presented more commonly with chronic blood loss. Delay in diagnosis was still a serious problem and weight loss remained an underestimated symptom, especially when combined with other upper gastrointestinal symptomology. The majority of tumours were adenocarcinomas. Six patients had unusual tumours which had special therapeutic and prognostic implications. The results of the above study are compared with the European experience of the management of malignant gastric tumours.

Five commercial enzyme linked immunosorbent assay kits for toxoplasma specific IgM antibody

Five commercially available enzyme linked immunosorbent assay (ELISA) kits for the detection of specific IgM against Toxoplasma gondii were evaluated in a three centre study and results compared with those of the Public Health Laboratory Service ELISA for Toxoplasma IgM (PHL IgM ELISA). Fifty selected sera were tested by all the methods (Toxo-M, Captia Toxo-M EIA, Toxo Enz M EIA, Toxonostika IgM EIA, Sopazyme Toxo IgM EIA) at the three reference centres in England and Wales and 177 routine sera by all the methods in one or other of the centres. Ten of the 50 selected sera contained autoimmune antibodies but no specific IgM and 29 had toxoplasma specific IgM detectable by the PHL IgM ELISA. The kits were assessed for their specificity and sensitivity compared with the PHL IgM ELISA, and the percentage coefficient of variation for binding to the solid phases was determined. They were also rated subjectively by the staff performing the assays and an overall impression of each kit was gained by allocating scores of several criteria. There was quite close agreement among the results obtained with all five commercial assays and the PHL IgM ELISA, although some of the sera pre-selected as being potentially problematic showed the limitations of some of the assays.

Rapid indirect enzyme linked immunosorbent assay (ELISA) for detecting antitoxoplasma IgG: comparison with dye test

A rapid and simple enzyme linked immunosorbent assay (ELISA) for the detection of specific IgG against Toxoplasma gondii was compared with the dye test on 533 serum samples. In general, results were comparable but not with sera that contained high concentrations of toxoplasma specific IgM or that had been heated at 56 degrees C. There were no false positive results with sera containing rheumatoid factor or anti-nuclear factor. It is concluded that if a dye test is not to be performed then the serum should be tested for both toxoplasma specific IgG and IgM to avoid misleading results. Heat inactivated serum should also not be tested in this type of specific IgG assay.

Enzyme-linked immunosorbent assays for the measurement of specific antibodies in experimentally induced ovine toxoplasmosis

Tachyzoites of the RH strain of Toxoplasma gondii were inoculated intravenously into sheep following which serum samples were collected at approximately weekly intervals for 9 months. The sera were examined by the toxoplasma dye test and two enzyme-linked immunosorbent assays (ELISA) specifically developed for investigations of ovine toxoplasmosis. One was an antibody class capture assay for the detection of anti-toxoplasma specific IgM, the other an indirect assay which detected anti-toxoplasma IgG. Some of the sheep had antibodies to toxoplasma prior to inoculation but none had specific IgM. Sera collected 17 days after inoculation showed that all had raised specific antibody levels but the only sheep that produced specific antitoxoplasma IgM were those that were initially without any antibody. Specific IgM could be detected in all these particular sheep for at least 1 month after infection and up to 3 months in some. Specific IgG persisted at high levels for at least 3 months and could still be detected at moderate levels for at least 9 months. The ELISA methods described are simple to perform and could clearly distinguish between previous infection and this experimental infection with Toxoplasma gondii.

Public Health Laboratory Service enzyme linked immunosorbent assay for detecting Toxoplasma specific IgM antibody

An enzyme linked immunosorbent assay (ELISA) based on the antibody class capture method for the detection of specific IgM against Toxoplasma gondii, using the microtitre plate format, was developed. Antigen binding was detected using a monoclonal antibody, CIE3, conjugated to horseradish peroxidase. Prior mixing of the conjugate and antigen improved the stability of these reagents as well as removing an incubation stage from the assay. The incubation time of less than four hours permits a rapid throughput of specimens. Using the assay, a total of 163 sera were examined in a three centre study and good agreement was found. Results were expressed as arbitrary enzyme immunoassay units (EIUs) against a freeze dried standard. Throughout the study the standard serum showed a coefficient of variation less than 10% across the microtitre plate. By measuring IgM titres in patients having toxoplasmic lymphadenopathy with a known date of onset, IgM class antibodies were shown to peak at two months, persisting for about six months. In addition, a case of laboratory acquired toxoplasmosis was monitored. Sera shown to contain rheumatoid factor and antinuclear factor did not give false positive results. This rapid, robust, and simplified assay is used by the Public Health Laboratory Service Toxoplasma Reference Units and will provide a standard with which other assays can be compared.