Digit Bias Research Articles

Population health management for hypertension - building it into the system

Purpose of the study: Hypertension is prevalent, expensive and a major contributor to cardiovascular mortality. There are numerous recommended hypertension practice guidelines and algorithms. However, population management is the key and can be achieved at all levels in health care through a systems approach. Statement of the methods used: InterMed a multispecialty group practice in Portland Maine with 75,000 patients integrates a population health management approach at the clinical level. Using Clinical Microsystems (front-line units comprised of a small group of people that provide health care) and ‘‘Working from the ground up’’ we have a structured approach to organizational improvement and a ‘‘laboratory’’ for finding and refining successful practices for hypertension management that can be adopted across the organization. Summary of results: InterMed has implemented full utilization of data at all levels of care including: Terminal digit bias data for accurate BP measurement and assessment of staff training Hypertension patient panel data Population management and performance metrics tied to public reporting InterMed’s systems approach has allowed us to adopt, test and modify an algorithm/practice guidelines for hypertension management. Components which include: Established a prescription refill protocol which reduces delays in BP medication refills NP/PA hypertension experts to see patients in follow up for medication titration Provide 24 hour blood pressure monitor as appropriate Home BP monitoring and patient engagement in self-management Establish Hypertension Specialty Practice for resistant hypertension and challenging cases (InterMed is the first health system in Maine to have a primary care physician certified as hypertension specialist) Conclusions reached: Hypertension is associated with increased risk of cardiovascular events, particularlystroke, heart failure, and kidney disease. Improved control of blood pressure leads to a proven reduction in cardiac events. Evidence supports an organized, comprehensive system of regular population review and intervention to improve the management of hypertension.

Perceptions of care on anti-hypertensive medications adherence among blacks

Purpose of the study: Hypertension is prevalent, expensive and a major contributor to cardiovascular mortality. There are numerous recommended hypertension practice guidelines and algorithms. However, population management is the key and can be achieved at all levels in health care through a systems approach. Statement of the methods used: InterMed a multispecialty group practice in Portland Maine with 75,000 patients integrates a population health management approach at the clinical level. Using Clinical Microsystems (front-line units comprised of a small group of people that provide health care) and ‘‘Working from the ground up’’ we have a structured approach to organizational improvement and a ‘‘laboratory’’ for finding and refining successful practices for hypertension management that can be adopted across the organization. Summary of results: InterMed has implemented full utilization of data at all levels of care including: Terminal digit bias data for accurate BP measurement and assessment of staff training Hypertension patient panel data Population management and performance metrics tied to public reporting InterMed’s systems approach has allowed us to adopt, test and modify an algorithm/practice guidelines for hypertension management. Components which include: Established a prescription refill protocol which reduces delays in BP medication refills NP/PA hypertension experts to see patients in follow up for medication titration Provide 24 hour blood pressure monitor as appropriate Home BP monitoring and patient engagement in self-management Establish Hypertension Specialty Practice for resistant hypertension and challenging cases (InterMed is the first health system in Maine to have a primary care physician certified as hypertension specialist) Conclusions reached: Hypertension is associated with increased risk of cardiovascular events, particularlystroke, heart failure, and kidney disease. Improved control of blood pressure leads to a proven reduction in cardiac events. Evidence supports an organized, comprehensive system of regular population review and intervention to improve the management of hypertension.

Rounding of birth weights in a neonatal intensive care unit over 20 years: an analysis of a large cohort study

ObjectiveTo determine the frequency of birth weight digit preference for infants admitted to a large neonatal intensive care unit (NICU), the scale of rounding and its dependence on birth weight,...

Correlates of Digit Bias in Self-reporting of Cigarette per Day (CPD) Frequency: Results from Global Adult Tobacco Survey (GATS), India and its Implications

Cigarette per day (CPD) use is a key smoking behaviour indicator. It reflects smoking intensity which is directly proportional to the occurrence of tobacco induced cancers. Self reported CPD assessment in surveys may suffer from digit bias and under reporting. Estimates from such surveys could influence the policy decision for tobacco control efforts. In this context, this study aimed at identifying underlying factors of digit bias and its implications for Global Adult Tobacco Surveillance. MATERIALS OR METHODS: Daily manufactured cigarette users CPD frequencies from Global Adult Tobacco Survey (GATS)--India data were analyzed. Adapted Whipple Index was estimated to assess digit bias and data quality of reported CPD frequency. Digit bias was quantified by considering reporting of '0' or '5' as the terminal digits in the CPD frequency. The factors influencing it were identified by bivariate and logistic regression analysis. The mean and mode of CPD frequency was 6.7 and 10 respectively. Around 14.5%, 15.1% and 15.2% of daily smokers had reported their CPD frequency as 2, 5 and 10 respectively. Modified Whipple index was estimated to be 226.3 indicating poor data quality. Digit bias was observed in 38% of the daily smokers. Heavy smoking, urban residence, North, South, North- East region of India, less than primary, secondary or higher educated and fourth asset index quintile group were significantly associated with digit bias. The present study highlighted poor quality of CPD frequency data in the GATS-India survey and need for its improvement. Modeling of digit preference and smoothing of the CPD frequency data is required to improve quality of data. Marketing of 10 cigarette sticks per pack may influence CPD frequency reporting, but this needs further examination. Exploring alternative methods to reduce digit bias in cross sectional surveys should be given priority.

Consistency of daily cigarette smoking amount in dependent adults.

Self-reported cigarettes per day (CPD) is a very common screening as well as dependent or independent measure in clinical and nonclinical research on smoking, but the consistency of CPD across days in dependent smokers is uncertain. Adult dependent smokers (N = 357; 170 men, 187 women) retrospectively reported "usual" CPD at screening and then prospectively self-monitored CPD on 3 consecutive days of 1 week during an ad libitum baseline period. Participants were those recruited for later tests of brief medication effects in those with high (n = 170) versus low (n = 187) interest in quitting smoking soon (within 3 months). Consistency was determined by intraclass correlation (ICC). Prospective daily CPD was generally consistent (ICC = 0.78, 95% CI of 0.74-0.81), but CPD changed (increased or decreased) by 5 cigarettes/day or more in 40% of participants and by at least 10/day in 10%. Consistency in CPD was greater in higher dependent smokers and in women with low (vs. high) quit interest, but consistency tended to be greater in men with high (vs. low) quit interest. Although retrospectively reported CPD at screening was consistent with the overall mean for prospectively monitored daily CPD, 15% of participants differed by at least 5/day between methods, and digit bias was twice as likely with retrospective versus prospective CPD, which was at chance levels. Understanding variability in CPD may improve knowledge of dependence and factors that foster or discourage daily smoking amount, but precise assessment of daily CPD likely requires prospective monitoring.

Role of ambulatory and home blood pressure recording in clinical practice.

Because of shortcomings of the office blood pressure (BP) measurement in individuals with hypertension (eg, white coat and masked hypertension effects, terminal digit bias, and large variability in BP among a small number of readings), use of out-of-office blood pressure measurements has become more common in clinical practice. The presence of the syndromes of white-coat and masked hypertension creates the concern that the office BP measurements are not reflective of an individual patient's true BP values. Home (or self) and ambulatory BP assessments have been used in numerous types of clinical trials and have demonstrated their usefulness as reliable research and clinical tools. In this article, we review the recent literature on the benefits and limitations of home (self) and ambulatory monitoring of the BP in clinical practice. In particular, how it relates to the diagnosis of patients with various presentations of hypertension and to cardio-vascular outcomes with long-term follow-ups of population cohorts.

How many cigarettes did you smoke? Assessing cigarette consumption by global report, time-line follow-back, and ecological momentary assessment.

This study evaluated and compared several methods of assessing daily cigarette consumption. Comparison of measures of daily cigarette consumption from several sources, from 232 smokers entering a smoking cessation program. Global reports of average smoking, Time-Line Follow-Back (TLFB) recall for the week preceding the study (premonitoring TLFB), 2 weeks' cigarette recordings using electronic diaries and ecological momentary assessment (EMA), and TLFB recall of smoking during EMA (monitored TLFB). Global reports and premonitoring TLFB showed severe digit bias: six times as many values as expected were rounded at 10. Monitored TLFB also showed substantial digit bias (four times). EMA data showed none. EMA averaged 2.6 cigarettes lower than monitored TLFB, but exceeded TLFB on 32% of days. Across days, EMA and TLFB only correlated 0.29. Daily variations in TLFB did not correlate with variations in carbon monoxide (CO) measures taken on 3 days, but EMA measures did; among participants whose CO varied, r = .69. CO correlated with EMA cigarettes recorded in the preceding 2 hours, suggesting timely recording of cigarettes. TLFB measures are limited for precise assessment of cigarette consumption. EMA measures appear to be useful for tracking smoking, and likely other health-relevant events.

Timeline follow-back versus global self-reports of tobacco smoking: A comparison of findings with nondaily smokers.

Methods assessing nondaily smoking are of concern because biochemical measures cannot verify self-reports beyond 7 days. This study compared 2 self-reported smoking measures for nondaily smokers. A total of 389 college students (48% women, 96% White, mean age=19 years) smoking between 1 and 29 days out of the past 30 completed computer assessments in 3 cohorts, with the order of administration of the measures counterbalanced. Values from the 2 measures were highly correlated. Comparisons of timeline follow-back (TLFB) with the global questions for the total sample of nondaily smokers yielded statistically significant differences (p<.001), albeit small, between measures with the TLFB resulting on average in 2.38 more total cigarettes smoked out of the past 30 days, 0.46 fewer smoking days, and 0.21 more cigarettes smoked per day. Analyses by level of smoking showed that the discordance between the measures differed by frequency of smoking. Global questions of days smoked resulted in frequent reporting in multiples of 5 days, suggesting digit bias. Overall, the 2 measures of smoking were highly correlated and equally effective for identifying any smoking in a 30-day period among nondaily smokers.

Variation in recorded blood pressure terminal digit bias in general practice

This study aims to identify the extent of terminal digit bias in routinely recorded blood pressures (BP) across a number of different general practices and report on changes in terminal digit bias over a 10-year period. It also explores the effect this may have had on the mean recorded BP in this population. BP records were taken from The Health Improvement Network database containing anonymized patient records from information entered by UK general practices in the financial years 1996-1997 to 2005-2006. The proportion of measurements ending in zero and the mean BP readings were calculated for each practice and for each year of data.Over this 10-year period the percentage of systolic BPs with zero terminal digits fell from 71.2 to 36.7% and mean recorded BP fell from 152.3 to 145.3 mm Hg. Correcting the BPs to remove terminal digit bias indicates a 2-3 mm Hg underestimation of the mean population systolic BP over this period. The between-practice variation in the percentage of zero terminal digit readings increased from 3.5 to 6.5 s.d. Although it is welcome to see a reduction in terminal digit bias, it is worrying to see the increase in variation between practices. There is evidence that terminal digit bias may lead to potential misclassification and inappropriate treatment of hypertensive patients. The increase in variation observed may therefore lead to an increased variation in the quality of care given to patients.

Blood Pressure Measurement Education and Evaluation Program improves measurement accuracy in community‐based nurses: A pilot study

Pilot study was developed to determine if a blood pressure measurement training program would improve guideline knowledge and technique in community-based nurses (n= 6). American Heart Association guidelines were used to develop the Blood Pressure Measurement Education and Evaluation Program (BEEP). Data on guideline knowledge, device quality, measurement technique, terminal digit bias, range of error, and attitude of change were collected prior and after BEEP. BEEP development was feasible and acceptable. The device score was 100%. Knowledge improved but not statistically significant (p= 0.64), as did terminal digit bias. Technique prior to BEEP was poor (T= 15) but improved significantly after BEEP (T= 26 on a scale of 32, p= 0.0006). Range of error decreased but was only significant in the diastolic pressure (p= 0.02). BEEP is feasible. Baseline blood pressure measurement technique is poor in community-based nurses. Our study suggests that this poor technique can benefit from an educational program and result in improved blood pressure measurement accuracy.

Limited (6-h) ambulatory blood pressure monitoring is a valid replacement for the office blood pressure by trained nurse clinician in the diagnosis of hypertension

To assess the ability of limited ambulatory blood pressure monitoring as a valid replacement for office blood pressure measurement done to American Heart Association criteria in diagnosing hypertension. In all, 105 adults, who had been referred for limited ambulatory blood pressure monitoring, participated in the study. Limited ambulatory blood pressure monitoring consisted of 6 h of blood pressure measurement while ambulatory at the Mayo Clinic, using a SpaceLabs 90207 (SpaceLabs Medical, Issaquah, Washington, USA) collecting six readings per hour for the period of observation. The study participants gave consent for three additional consecutive office blood pressure measurements, using a validated aneroid device, done to American Heart Association criteria, by a single hypertension nurse specialist. Mean systolic blood pressure by limited ambulatory blood pressure monitoring was 137.9+/-14.2 mmHg and for the nurse, 137.9+/-20.1 mmHg. Mean diastolic blood pressure by limited ambulatory blood pressure monitoring was 81.5+/-9.7 mmHg and for the nurse, 74.3+/-11.9 mmHg. The intermethod difference for systolic blood pressure was 0.03+/-12.5 mmHg and diastolic blood pressure, -7.2+/-8.0 mmHg. Using <140/90 as criteria factor, limited ambulatory blood pressure monitoring and the trained nurse agreed 77% of the time on whether the patient was hypertensive. This agreement increased to 81% if the participant's referral blood pressure was >or=140/90. Limited ambulatory blood pressure monitoring is an excellent replacement for office blood pressure, done to American Heart Association criteria, in diagnosing hypertension. This avoids issues of variability introduced by the observers, such as digit preference and bias, and increases reproducibility of blood pressure measurements. The appropriate normal value for limited ambulatory blood pressure monitoring is <140/90 mmHg compared with <135/85 mmHg used in 24-h ambulatory blood pressure monitoring.

Validation of the timeline follow-back in the assessment of adolescent smoking

The timeline follow-back instrument (TLFB) is a valid and reliable method of quantifying alcohol use patterns. The use of this instrument has been expanded to assess other behaviors, such as drug use, sexual behavior, binge eating, and panic attacks. Some evidence for the validity and reliability of this assessment instrument has emerged in the area of adult smoking. However, to date, there is no published evidence of its reliability and validity in the assessment of adolescent smoking. The purpose of this study is to present early evidence of the utility of the TLFB to collect information on adolescent smoking behavior. Through secondary data analysis of four studies on adolescent smokers, we examined the associations between the TLFB and measures of dependence, smoking history, respiratory symptoms, and saliva cotinine. Moreover, we examined the stability of the TLFB data across two 15-day time periods. Results provide preliminary evidence of the validity and reliability of the TLFB in the assessment of adolescent smoking. In particular, the TLFB instrument offered important data on the heterogeneity of adolescent smoking patterns beyond a global measure of cigarettes per day, and the reduction of digit bias. Implications of these findings for the assessment of adolescent smoking are discussed.

Terminal digit bias in a specialty hypertension faculty practice.

Traditional blood pressure (BP) methodology is subject to observer error such as terminal digit preference and single number preference leading to inaccuracies in measurement. A high percentage (60-90%) of terminal BP readings digit being zero has been reported from general medical- and hospital-based clinics. This study examined terminal digit preference in a hypertension specialty practice and assessed clinical factors that may be associated with zero preference in this setting. A retrospective chart review of patients presenting to the hypertension clinic at the University of Connecticut Health Center during the month of September 2001 was performed. Data were extracted on age, gender, height, weight, treatment status, and systolic and diastolic BP measurements taken by nursing staff and attending physicians. Terminal digit preference was apparent in BP readings taken by both nursing staff and physicians. Zero was the terminal systolic BP digit in 40% of readings taken by the nursing staff and 31% of readings taken by physicians. For diastolic BP readings, the percentages were 23 and 36%, respectively. Nurses also recorded 43% of diastolic BP readings with terminal digit 2. Age was significantly higher in those persons in whom the physician diastolic BP terminal digit was zero than in those with nonzero terminal digits (67+/-14 vs 59+/-18 years, P=0.008). Body mass index was lower in the patient group with diastolic terminal digit zero bias compared to those with nonzero terminal digits (28+/-5 vs 32+/-6 kg/m(2), P=0.02). In conclusion, although the frequency of zero digit preference did not reach the 60-80% levels found in previous studies, there was evidence of terminal digit preference in the systolic and diastolic measurements taken by nursing staff and attending physicians in a specialist hypertension clinic. We believe that the lower levels of terminal digit preference observed are an effect of increased training in proper BP measurement and technique. However, the observed bias in measurement even in a hypertension unit argues for regular monitoring and feedback to minimize such errors.

Practice audits: reliability of sphygmomanometers and blood pressure recording bias.

It is well established that numerous errors, biases and omissions in recording blood pressure exist. This study had two objectives. Firstly, to measure the accuracy of sphygmomanometers used in general practice and secondly to assess digit bias in blood pressure recording. This study was carried out in the then Northfield PCG, which comprised 18 practices and 67 GPs. A total of 131 mercury and aneroid sphygmomanometers were tested for accuracy by a trained technician in accordance with the methods specified in BS 2743 (1990). Accuracy was defined as an error of greater than 10 mm Hg. The second part of the methodology involved undertaking an audit of the proportion of registered patients aged 35-80 years who had their blood pressure measured within the last 5 years by members of the Primary Health Care Team. The results were that of the mercury and aneroid sphygmomanometers tested, 17% were inaccurate. Of these, 4% recorded an error greater than 10 mm Hg. One percent of mercury and 10% of aneroid sphygmomanometers recorded an error greater than 10 mm Hg respectively. Sixteen (12%) sphygmomanometers were so deteriorated (air leaks, dirt in mercury) that the researcher suggested their immediate withdrawal from service. The results of the blood pressure recording audit suggested digit bias of both systolic and diastolic recordings to the nearest 10 mm Hg. This study suggests that sphygmomanometers used in general practice are very likely to be inaccurate and some may well be so deteriorated that they should be withdrawn from service. The results of the blood pressure audit showed digit bias in systolic and diastolic readings to the nearest 10 mm Hg. The implications for clinical care-both over diagnosis and under diagnosis-although not assessed are likely to be appreciable. PCG Clinical Governance teams in conjunction with Practice Clinical Leads must address these basic issues.

Terminal digit bias in blood pressure measurement is reduced but not eliminated in a specialist hypertension practice

Terminal digit bias in blood pressure measurement is reduced but not eliminated in a specialist hypertension practice

Terminal digit preference, random error, and bias in routine clinical measurement of blood pressure

We examined the presence, magnitude, and consequences of systematic and random errors caused by terminal digit preference in the measurement of highest systolic blood pressure during prenatal visits in 28,841 non-referred pregnant women who delivered between 1 January 1982 and 31 March 1990. In the overall distribution of terminal digit readings, 78% were read to 0, 15% to even digits other than 0, 5% to 5, and only 2% to odd digits other than 5. This preference for 0's was consistent across the entire distribution of blood pressure and for a variety of maternal characteristics.The relative frequency of the cutoff value of 140 mmHg (i.e. the percentage of readings on 140 mmHg) within the range containing the value (i.e. 138–142 mmHg) was similar to the relative frequency of other multiples of 0. This was true whether the comparison was made in the overall study sample, or in a pre-selected low-risk subgroup or high-risk subgroup, indicating no systematic bias. On the other hand, a strong tendency to read blood pressure values to the nearest 0 had a marked effect on the classification of hypertension. Changing the definition of hypertension from ⩾/140 mmHg to > 140 mmHg produced a reduction in prevalence of hypertension from 25.9 to 13.3% in the overall study sample, from 15.4 to 6.3% in the low-risk subgroup, and from 43.3 to 25.3% in the high-risk subgroup.Epidemiologic studies that compare prevalences of hypertension in different populations based on routine clinical measurement of blood pressure and a single cutoff point should assess the consequences of terminal digit preference in defining hypertension. The relative frequency and changing cutoff point approach might be helpful in evaluating the existence and consequences of systematic bias and random error caused by terminal digit preference in other routine clinical and laboratory measurements as well.

Digit Bias in Measuring and a Device to Overcome It

5W5 HENEVER measurements are made by comparing the position of the boundary of an object with a graduated scale, as in measuring fish, even with the aid of pointers or cross hairs, there is a tendency, differing with observers, to favor certain digits. With trained observers carefully using good instruments, this bias should be slight. In the vast majority of instances where the results of groups of measurements are reduced to averages, it is of no consequence. Where the measurements are assembled into frequency distributions it may introduce artificial irregularities which may be bothersome when significance is to be attached to the shape of the curve. The irregularities can be reduced and sometimes obliterated by appropriate grouping into class intervals, or by mathematical smoothing. But when the frequency distribution is to be compared to theoretical curves by critical statistical methods such as the chi square test, such bias-induced irregularities form a serious, if not insurmountable, obstacle. This became obvious in my work on a series of tens of thousands of measurements of the Pacific sardine, or pilchard, Sardinops caerulea, accumulated over a period of years by a number of observers of the California Division of Fish and Game, and kindly loaned to the United States Fish and Wildlife Service for a special analysis involving curve fitting. These measurements had been made carefully by trained observers with the aid of a measuring board equipped with a sliding rider which could be placed so that its cross hair or thread would be over the point to be measured on the fish, running from there to a point over a rule which was graduated in millimeters, and the readings were made to the nearest millimeter. The length of the fish ranged from 150 to 300 mm. When the measurements were grouped according to observer and classified according to the final digit of the reading, it was apparent that each person had a different bias pattern. Some of these are shown in fig. 1. An example of odd-even bias is given by A. The probabilty (P), computed by the chi square method, that purely random variations would exceed the observed variations from the mean, is 0.002. A case of bias in favor of five and zero and against four and seven is given by B (P = <0.001). The three curves were of measurements by the same observer and grouped by time periods. During the first two months, C, there was a marked bias favoring zero and five mainly at the expense of one, four, six, and nine (P = <0.001). At the end of this time the observer must have noted its existence, and attempted to avoid it, for the third month, C' (P = <0.001), exhibits the opposite of the former bias with respect to zero and five. Apparently noting this also, the observer again changed his habits during the succeeding three months, C (P = <0.001), practically eliminating bias as concerns zero and five, though retaining significant bias, now favoring three and eight mainly at the expense of four and seven. Such biases can be eliminated by incorporating in the measuring mechanism a mechanical selector. The one devised for the sardine measuring board