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Biomedical subjects

R J Herbert

Publications and source records attributed to R J Herbert.

At least 19 recordsLinked to original sources
PubMed2001

Patterns of disease-modifying antirheumatic drug use, medical resource consumption, and cost among rheumatoid arthritis patients.

We compared medical resource use and costs among rheumatoid arthritis (RA) patients receiving alternative disease-modifying antirheumatic drugs (DMARDs). The cohort study used data from a managed care organization. Health plan members who were prescribed DMARD therapy for at least 2 consecutive months, were age 18 years or older, had at least 6 months of DMARD-free enrollment prior to the first DMARD, and had a diagnosis of RA before or during the first month of DMARD were eligible. Median duration of initial DMARD therapy was 10 months overall: 11 months for hydroxychloroquine (n = 252), 15 months for methotrexate (n = 185), 5 months for sulfasalazine (n = 49), and 5 months for other mono/combination therapy (n = 85) (p < 0.0001). The average monthly cost of care was $853, of which $294 (34%) was for RA-coded medical services. In multivariate analyses, monthly RA-coded costs varied significantly by initial DMARD. RA costs and duration of initial therapy varied significantly by initial DMARD.

Antirheumatic Agents↗
PubMed2001

Ethylene induces cell death at particular phases of the cell cycle in the tobacco TBY-2 cell line.

It was examined whether ethylene induces programmed cell death in a cell cycle-specific manner. Following synchronization of the tobacco TBY-2 cell line with aphidicolin and its subsequent removal, ethylene was injected into the head space of 300 cm(3) culture flasks at 0 h or 3.5 h later and cells were sampled for 26 h. There were significant increases in cell mortality at G(2)/M in both the 0 h and 3.5 h ethylene treatments, and for the latter treatment, another peak in S-phase. The effect at G(2)/M was greater in the 3.5 h treatment, but was ameliorated by the simultaneous addition of silver nitrate (1.2 microM). In addition, the 3.5 h ethylene treatment resulted in a 1 h delay in the characteristic rise in the mitotic index following aphidicolin-induced synchrony. The addition of silver nitrate alone (1.2 microM), also delayed the entry of cells into mitosis but had no effect on cell cycle length compared with the controls (14 h throughout all treatments) but it induced a peak of mortality 2.5 h after its addition. Nuclear shrinkage was also a characteristic feature of dying cells at G(2)/M. Using Apoptag, an in situ apoptosis detection kit, nuclear DNA fragmentation was observed in the TBY-2 cells which were often isolated on the end of a filament of normal cells. In the 3.5 h ethylene treatment, a marked increase was noted in the percentage of such cells at the G(2)/M transition compared with the controls. Hence, the data show cell death occurring at a major phase transition of the cell cycle and the observations of nuclear shrinkage, isolation of dying cells and nuclear DNA fragmentation suggest a programmed mechanism of cell death exacerbated by ethylene treatment.

Aphidicolin↗
PubMed2000

Interference from multi-dimensional objects during feature and conjunction discriminations.

Feature discrimination performance within an attended object and interference from irrelevant, multi-dimensional objects (distractors) were examined in a two-choice, response compatibility paradigm. Results showed that the amount of interference by multi-dimensional distractors was dependent on three factors: (1) the discriminability of the incompatible, task-relevant distractor features; (2) the number of incompatible, task-relevant distractor features; and (3) whether the task-relevant, incompatible features matched the task goals. The most interesting finding was that additive priming effects were found for multiple, task-relevant features that matched the task goals, whether these features were present in the attended object or in the ignored object. Models that assume that each task-relevant feature primes its corresponding decision/response asynchronously and that this priming is combined to meet a decision/response criterion (at least when attended) can account for distractor interference during conjunction discriminations. Implications of these findings for feature integration models, template models, and a response selection model are discussed.

Adult↗
PubMed2000

The determination time of the carpel whorl is differentially sensitive to carbohydrate supply in Pharbitis nil.

A shoot apical meristem is florally determined if, following its removal from an induced plant, it flowers when cultured in non-inductive conditions. Determination times were measured in the short-day plant Pharbitis nil to examine whether floral whorls are determined simultaneously or sequentially. Shoot apices were excised at daily intervals following a 48-h dark-inductive treatment, cultured in non-inductive conditions for 4 weeks in continuous light, and the number of floral organs scored. The culture medium was White's supplemented with sucrose, glucose (Glc), fructose (Fru), or 1:1 Glc:Fru at 2% (w/v), 4% (w/v), or 6% (w/v) or sugar-mannitol combinations of osmotic potentials equivalent to 4% (w/v) or 6% (w/v). The minimum whorl determination time was 1 d for sepals, petals, and stamens regardless of carbon supply. However, for carpels it varied remarkably from 5 d on sucrose, to 2 to 3 d on Fru or Glc:Fru, to 1 d for 2% (w/v) and 6% (w/v) Glc. Therefore, depending on the carbon supply, the carpel whorl was determined at the same time or after the outer whorls. Generally, these effects could not be reproduced on the sugar-mannitol treatments.

Carbohydrate Metabolism↗
PubMed2000

One-year costs of second-line therapies for depression.

BACKGROUND: We compared patterns of medical resource utilization and costs among patients receiving a serotonin-norepinephrine reuptake inhibitor (venlafaxine), one of the selective serotonin reuptake inhibitors (SSRIs), one of the tricyclic agents (TCAs), or 1 of 3 other second-line therapies for depression. METHOD: Using claims data from a national managed care organization, we identified patients diagnosed with depression (ICD-9-CM criteria) who received second-line antidepressant therapy between 1993 and 1997. Second-line therapy was defined as a switch from the first class of antidepressant therapy observed in the data set within 1 year of a diagnosis of depression to a different class of antidepressant therapy. Patients with psychiatric comorbidities were excluded. RESULTS: Of 981 patients included in the study, 21% (N = 208) received venlafaxine, 34% (N = 332) received an SSRI, 19% (N = 191) received a TCA, and 25% (N = 250) received other second-line antidepressant therapy. Mean age was 43 years, and 72% of patients were women. Age, prescriber of second-line therapy, and prior 6-month expenditures all differed significantly among the 4 therapy groups. Total, depression-coded, and non-depression-coded 1-year expenditures were, respectively, $6945, $2064, and $4881 for venlafaxine; $7237, $1682, and $5555 for SSRIs; $7925, $1335, and $6590 for TCAs; and $7371, $2222, and $5149 for other antidepressants. In bivariate analyses, compared with TCA-treated patients, venlafaxine- and SSRI-treated patients had significantly higher depression-coded but significantly lower non-depression-coded expenditures. Venlafaxine was associated with significantly higher depression-coded expenditures than SSRIs. However, after adjustment for potential confounding covariables in multivariate analyses, only the difference in depression-coded expenditures between SSRI and TCA therapy remained significant. CONCLUSION: After adjustment for confounding patient characteristics, 1-year medical expenditures were generally similar among patients receiving venlafaxine, SSRIs, TCAs, and other second-line therapies for depression. Observed differences in patient characteristics and unadjusted expenditures raise questions as to how different types of patients are selected to receive alternative second-line therapies for depression.

Adult↗
PubMed1999

Medical resource use and cost of venlafaxine or tricyclic antidepressant therapy. Following selective serotonin reuptake inhibitor therapy for depression.

OBJECTIVE: An analysis of administrative and claims data was performed to compare the resource use and costs to a managed-care organisation of venlafaxine, a serotonin and norepinephrine reuptake inhibitor (SNRI), versus tricyclic antidepressant (TCA) therapy, after switching from a selective serotonin reuptake inhibitor (SSRI). DESIGN: One-year costs and frequencies of all medical services, and of services coded for depression, were compared between patients who received venlafaxine and TCA therapy as second-line therapy using bivariate and multivariate statistical analyses. SETTING: Data were obtained from 9 individual health plans with more than 1.1 million covered lives affiliated with a national managed-care organisation. PATIENTS AND PARTICIPANTS: Health plan members were included if they had a diagnosis of depression between July 1993 and February 1997. They also had to have at least 2 months of prescriptions for SSRI therapy followed by at least 2 months of venlafaxine or TCA therapy, and continuous enrollment in the plan from at least 6 months prior to 12 months following initiation of venlafaxine or TCA therapy. 188 patients who received venlafaxine and 172 patients who received TCAs met the inclusion criteria. MAIN OUTCOME MEASURES AND RESULTS: Patients who received TCAs were slightly but significantly older (43 vs 40 years) than venlafaxine recipients and, during 6 months prior to initiating therapy, had significantly higher mean costs coded for depression ($US451 vs $US311) and costs not coded for depression ($US4500 vs $US2090). Psychiatrists prescribed a significantly higher proportion of venlafaxine than TCA prescriptions (46.3 vs 25.0%). Prior to adjusting for confounding characteristics, during 12 months following initiation of therapy, mean depression-coded costs were significantly higher for venlafaxine than TCA recipients ($US1948 vs $US1396) and mean costs not coded for depression were significantly lower ($US4595 vs $US6677). Overall costs were not significantly different ($US6543 for venlafaxine vs $US8073 for TCA). Significant cost differences were observed with primary care physicians as initial prescribers of second-line therapy but not with psychiatrists. However, costs between the 2 groups were similar after adjusting for confounding variables, including prior 6-month costs and initial prescriber of second-line therapy. CONCLUSIONS: Payer costs are similar among patients receiving venlafaxine and TCA therapy following SSRI therapy. Higher costs of venlafaxine pharmacotherapy relative to TCA therapy may be offset by lower costs of other medical services. Differences in prescribing patterns and costs between primary care physicians and psychiatrists warrant further investigation.

Adult↗
PubMed1998

Medical-resource use for suspected tuberculosis in a New York City hospital.

OBJECTIVE: To compare resource use by diagnostic outcome among hospital admissions during which tuberculosis (TB) was suspected. DESIGN: Retrospective study based on chart review and microbiology laboratory data. SETTING: The department of medicine in a municipal hospital serving central Brooklyn, New York. PARTICIPANTS: We identified all adult admissions in 1993 during which TB was suspected. We assigned each admission to one of four mutually exclusive groups defined by the results of microbiological tests (acid-fast bacilli [AFB] smear and culture): culture-positive and smear-positive (C+S+); culture-positive and smear-negative (C+S-); culture-negative and smear-positive (C-S+); or culture-negative and smear-negative (C-S-). Each admission was divided into two separate periods to which the utilization of medical resources was assigned: the diagnostic and the postdiagnostic periods, which were separated by the date of receipt of the first definitive culture report. RESULTS: Data on 519 admissions (93 C+S+; 57 C+S-; 30 C-S+; and 339 C-S-) were analyzed. Although C+S+ were more likely than other groups to have an admitting diagnosis of TB, approximately one quarter of the admissions without TB (C-S+, C-S-) were admitted with the principal diagnosis of TB. For the four groups, C+S+, C+S-, C-S+, and C-S-, the respective rates of TB isolation and anti-TB treatment, and median lengths of isolation were 98%, 87%, and 34 days; 74%, 74%, and 7 days; 83%, 83%, and 15 days; and 44%, 29%, and 0 days. During the diagnostic period, the rate and length of isolation were similar in the AFB-smear-positive groups (C+S+ and C-S+). We estimated that admissions without culture-proven TB (C-S+ and C-S-) accounted for 3,174 (36%) of the 8,712 days of TB isolation expended and for 65% of the 16,671 days of anti-TB treatment. The vast majority of this resource consumption (2,737 [86%] of 3,174 days of isolation) occurred during the diagnostic period before a definitive culture result was known. CONCLUSIONS: Our results suggest that prolonged diagnostic uncertainty and misclassification of cases due to false-positive and false-negative smears are associated with substantial medical-resource consumption. New diagnostic modalities that reduce the period of diagnostic uncertainty could reduce the utilization of resources later found to be unnecessary.

Adult↗
PubMed1995

Economic impact of immunization against rotavirus gastroenteritis. Evidence from a clinical trial.

OBJECTIVE: To estimate the economic impact of immunization against rotavirus gastroenteritis in an infant population in the United States. DESIGN: Cost identification and break-even analyses from the perspective of society, nested within a phase 3, randomized, double-blind, placebo-controlled trial. PATIENTS: Infants (N = 1278), aged 6 to 22 weeks, enrolled during the summer and fall of 1991 and followed up until July 1, 1992. INTERVENTION: Immunization schedule of three doses of orally administered tetravalent or serotype 1 rhesus rotavirus vaccine, or placebo. MAIN OUTCOME MEASURES: Incidence of rotavirus gastroenteritis, total direct medical costs, direct nonmedical costs, and indirect costs of rotavirus and nonrotavirus gastroenteritis for the duration of the study and of any illness during 5 days after each dose. The cost of the vaccine was not included. RESULTS: Median total cost per infant among the 1187 infants who completed the immunization schedule was $9 in the tetravalent vaccine group, $9 in the serotype 1 vaccine group, and $49 in the placebo group (P = .01). Rotavirus gastroenteritis occurred in 195 infants (16%): 13% (51/398) in the tetravalent group, 12% (47/404) in the serotype 1 group, and 25% (97/385) in the placebo group (P < .0001). Of infants with an episode of rotavirus gastroenteritis, the proportion who incurred cost during the episode and the median cost during the episode did not differ by treatment group. The baseline net cost savings for treatment of rotavirus gastroenteritis and break-even cost of immunization were $11 per infant for the tetravalent vaccine and $12 for the serotype 1 vaccine. In sensitivity analysis, savings ranged from $40 to -$6, because of a large variance in the costs of rotavirus gastroenteritis. CONCLUSION: The results of the baseline analysis suggest that society should be willing to pay between $11 and $12 for immunization against rotavirus. It might be willing to pay an additional amount for the intangible benefits of reduced parental inconvenience or anxiety associated with this illness in infants.

Cost Savings↗
PubMed1994

The relationship of provider organizational status and erythropoietin dosing in end stage renal disease patients.

Controversy exists as to whether provider organizational characteristics such as profit status and setting are associated with the content of medical care or efficiency with which care is rendered. Following FDA approval of human recombinant erythropoietin (EPO) for use in clinical practice, Medicare approved coverage for beneficiaries in its end stage renal disease program and established a fixed payment per dose. Because cost of EPO administration varied positively with dose, providers could realize larger profit with prescription of smaller doses. We used Medicare claims data to assess EPO use by renal dialysis providers one year after FDA approval (June 1990) as a function of provider ownership (for-profit, not-for-profit, government agency) and setting (hospital-based, free-standing). Mean dose of EPO was 236 units greater (P = 0.0001) for not-for-profit freestanding facilities, 593 units greater (P = 0.0001) for government facilities, and 555 units greater for not-for-profit hospitals (P = 0.0001) than among for-profit freestanding providers. With fixed payment per dose of EPO, for-profit, freestanding providers prescribed EPO more often and administered smaller doses than not-for-profit or government providers, behavior that is consistent with profit maximization.

Ambulatory Care Facilities↗
PubMed1994

Effect of recombinant erythropoietin on hospital admissions, readmissions, length of stay, and costs of dialysis patients.

To examine the effects of recombinant human erythropoietin (rHuEPO) on hospital utilization, hospital costs, and Medicare reimbursements for hospital care, a longitudinal, matched cohort study was conducted using Medicare claims data of 23,806 Medicare-eligible, dialysis patients who received rHuEPO, did not have a transplant, and were alive for 18 mo or longer and 22,720 controls matched on age, sex, race, cause of ESRD, and dialysis modality. The relative odds (rHuEPO versus control) of admission for all causes and for specific causes over 9 mo, adjusted for admission in the prior 9 mo and the per patient change in total admissions, inpatient days, hospital costs, and Medicare hospital payments between the prior 9-mo period and the subsequent 9-mo period was examined. The adjusted relative odds (95% confidence interval) of admission (rHuEPO versus control) was: higher and statistically significant for all causes, 1.08 (1.03 to 1.14); seizure, 1.52 (1.28 to 1.75); vascular access revision, 1.11 (1.06 to 1.17), and heart failure, 1.17 (1.09 to 1.26); higher but not statistically significant for angina, 1.09 (0.99 to 1.20) and stroke, 1.08 (0.86 to 1.31); and lower but not statistically significant for myocardial infarction, 0.91 (0.72 to 1.10); peripheral vascular disease, 0.81 (0.60 to 1.02); anemia, 0.86 (0.56 to 1.17); and depression, 0.89 (0.37 to 1.40). The mean change per 1,000 patients in admissions was less by 38 (P = 0.03) because of fewer readmissions, and in days was 1,309 less (P < 0.001), for patients treated with rHuEPO versus controls. The mean change per patient in hospital costs was $371 less and was statistically significant (P = 0.03) and in Medicare hospital payments was $132 less but was not statistically significant (P = 0.43) for patients treated with rHuEPO versus controls. rHuEPO was associated with an increase in the probability of hospital admission (particularly admissions potentially related to adverse effects) but a decrease in readmissions, overall admissions, hospital days, and cost to hospitals in this cohort of patients surviving for 18 mo. Although not realized short term, Medicare savings from potential rHuEPO-related reductions in hospital care may be long term through future adjustments in diagnosis-related group-based hospital payment.

Adult↗
PubMed1993

Medicare payment policy and recombinant erythropoietin prescribing for dialysis patients.

The Medicare payment policy for recombinant human erythropoietin (rHuEPO) treatment for dialysis patients changed in January 1991 from a relatively fixed payment per treatment (allowed charge of $40 per < or = 10,000 units injected) to a more variable payment based on the amount of rHuEPO administered with each treatment (allowed charge of $11 per 1,000 units injected). This change provided an opportunity to examine how payment policy can effect the use, cost, and health outcome of a biotechnology product used in the dialysis population. In cross-sectional (n = 71,880 Medicare-entitled dialysis patients) and longitudinal (n = 29,088 Medicare-entitled dialysis patients) study designs, we used Medicare end-stage renal disease program and claims data in bivariate and multivariate analyses to examine the effect of the change in payment policy for rHuEPO on access to the biotechnology, dosing, costs, and hematocrit, including the prescribing patterns at for-profit versus not-for-profit providers. The observation period included several months before (July 1989 to December 1990) and 6 months after (January to June 1991) the change in Medicare payment policy. The mean dose per treatment during the initial and fourth month of therapy was low (2,742 [95% confidence interval, 2,703 to 2,781] units and 2,632 [95% confidence interval, 2,598 to 2,667] units, respectively, in June 1990) and increased 3.4% and 5.0%, respectively, in the next 6 months prior to the change in Medicare payment policy compared with 14.6% and 14.8%, respectively, in the 6 months following the change in payment policy. The average monthly allowed charge for rHuEPO per dialysis patient receiving rHuEPO decreased from $455 before the policy change to $349 immediately following the policy change, because the allowed charge per unit of rHuEPO was lower when payment became more dependent on the amount of rHuEPO administered with each treatment than when the payment was fixed at $40 per treatment. The average monthly allowed charge for rHuEPO increased to $375 in the sixth month following the change in payment policy as a result of the increase in dose and the new variable payment. The unadjusted and adjusted changes in mean hematocrit 6 months after the payment change were positive but clinically very small (0.3 and 0.2 percentage points, respectively).(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1993

Early dosing practices and effectiveness of recombinant human erythropoietin.

In a national longitudinal-cohort study of 59,462 end-stage renal disease (ESRD) patients, we examined dosing and effectiveness of erythropoietin (EPO) during the first year of its use in clinical practice (July 1989 through June 1990). In unadjusted and multivariate analyses of Medicare claims data, the mean dose of EPO prescribed was: relatively small and similar for initial and maintenance therapy, 2752 (95% confidence interval 2740 to 2764) and 2668 (95% confidence interval 2654 to 2682) units, respectively; lower when initial therapy was started later (591 units lower in September 1989 and 760 units lower in November 1989 vs. July 1989, P < 0.0001); lower by 135 units during initial therapy and by 116 units during maintenance therapy for females (who weigh less) compared to males (P < 0.001); and lower by 400 units for patients treated in for-profit versus not-for-profit centers. In multivariate analysis: hematocrit response was less and mean maintenance dose was 298 units and 621 units greater for patients whose ESRD was due to multiple myeloma and sickle cell disease, respectively, compared to those with hypertension-related ESRD (P < 0.01); and hematocrit response was logarithmically related to dose [hematocrit = 0.97 ln (dose), P < 0.0001]. Forty-four percent of patients had a hematocrit > or = 30 after four months of therapy. The percent of patients transfused during three month periods before and after therapy decreased from 20% to 5%, respectively (P < 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

Access to recombinant erythropoietin by Medicare-entitled dialysis patients in the first year after FDA approval.

OBJECTIVE: Examine access to recombinant human erythropoietin (rHuEPO) by dialysis-dependent end-stage renal disease (ESRD) patients during the first year after FDA approval for use in clinical practice and Medicare coverage. DESIGN: Longitudinal and cross-sectional claims data analyses. SETTING: All US providers of outpatient dialysis treatment. PATIENTS: 126,201 Medicare-entitled dialysis patients (approximately 93% of all US dialysis patients). OUTCOME MEASURES: Percentage of patients who received rHuEPO, odds of receiving rHuEPO according to patient characteristics, and cost of rHuEPO to Medicare. RESULTS: One year after FDA approval, 52% of all dialysis and 60% of in-center hemodialysis patients who regularly had Medicare-paid dialysis services received rHuEPO at a monthly cost to Medicare of $19 million (18% of Medicare ESRD outpatient expenditures and 6% of all ESRD program expenditures). Blacks were less likely than whites to receive rHuEPO (odds ratio, 0.88; 95% confidence interval, 0.86 to 0.91). Home peritoneal and hemodialysis patients were less likely than in-center hemodialysis patients to receive rHuEPO (odds ratios, 0.17 and 0.22, respectively; 95% confidence intervals, 0.16 to 0.17 and 0.20 to 0.24, respectively). Use of rHuEPO varied across geographic regions. The odds of receiving rHuEPO were lower for patients of male vs female sex, of ages 35 through 64 years vs less than 35 years and greater than 65 years, with a longer history of ESRD, with polycystic kidney disease vs other causes of ESRD, and receiving care in nonprofit vs for-profit facilities. First-month hematocrits were slightly higher (1.2 percentage points) for patients starting rHuEPO in the 12th month than in the first month after FDA approval. CONCLUSIONS: With prompt insurance coverage, the majority of Medicare-entitled dialysis patients received rHuEPO following widespread availability. Factors that may not be related to clinical need (race, setting of care, and geography) possibly influenced early patient access. More attention should be paid to monitoring the appropriate use of high-cost biotechnologic therapy.

Adolescent↗
PubMed1987

A four-year longitudinal study of dental student learning styles.

Based on research conducted simultaneously but independently in Europe, Australia, and North America, several new learning style inventories have been developed with well-recognized theoretical foundations and sound psychometric properties. One of the instruments, the Gregorc Learning Style Delineator, was used to study the perceived learning styles of 48 dental students as they proceeded through the four years of the curriculum. Students scored significantly higher on one of four possible learning style dimensions during each year of the curriculum. This dimension, the concrete sequential, is associated with the following learning style characteristics: preference for factual over abstract information, desire for a highly organized learning environment with considerable hands-on opportunity, but free from distractions or ambiguity about learning tasks. Students' preference for the concrete sequential dimension increased significantly as they progressed toward graduation, suggesting that the learning environment of the dental school actually served to reinforce the students' initial predisposition toward the concrete sequential orientation.

Curriculum↗
PubMed1986

A comparison of simulation programs for endodontic review.

Computer-Based Instruction (CBI) has been gaining increasing popularity in the health professions and especially in dental education, but its development is seldom problem-free. This paper describes a longitudinal study of endodontic simulations for senior dental students which employ latent image, computer-assisted video interactive (CAVI), and computer text instruction (CTI). Particular attention is devoted to developmental problems, use of time and manpower, and student performance on and reaction to the pilot test. Preliminary results of the pilot testing demonstrate favorable student performance on the computer-based mode, as well as an enthusiastic acceptance of this format. Future directions and goals of the study are included.

Computer-Assisted Instruction↗
PubMed1984

Effects of lecture information density on medical student achievement.

With the virtual explosion of biomedical information, the medical educator regularly faces a quandary regarding how much to include in the medical curriculum. Opinions differ regarding how much of the available information on a particular topic should be presented in a medical school lecture. To understand better the effect of lecture information density on learning by medical students, one of the authors gave a basic clinical lecture only or clinical lectures with varying amounts of semirelated information. Tests which measured only retention of the basic material were given before lecture attendance, immediately after the lecture, and 15 days later. The results indicated that increasing the information density of a lecture reduced retention of the basic information. The memory loss apparently was due to information presented late in the lecture displacing facts learned by the students earlier in the same hour. The data suggest that lectures to medical students are more effective aids to learning when the information density is limited to a few main points that are "essential to know."

Achievement↗