Neural network-assisted ("NNA") analysis of cervical smears: pooled effectiveness results and economic analysis

Objective: To determine the sensitivity of cervical cancer smear screening with neural network-assisted ("NNA") rescreening.Methods: The Papnet system of NNA analysis of cervical smears has been in clinical use worldwide for over 3 years and has been the subject of over 22 published manuscripts reporting on data from over 202,000 smears. This investigation reviewed the results of these studies and classified each study according to study design using a systematic protocol based on reference validation, diagnostic threshold for abnormal, and outcome metric. This classification taxonomy allowed for weighted (based on number of cases in each study) pooling of studies for each study design class. The pooled effectiveness metrics were used to derive the sensitivity of cervical cancer screening with NNA rescreening, using a baseline unassisted screening sensitivity of 85%. Other effectiveness metrics determined by this analysis include NNA's sensitivity as a primary screener, comparisons with primary unassisted screening, and comparisons of NNA rescreening and unassisted rescreening.Results: Analyses of the weighted, pooled mean estimates for each of the principal outcome metrics indicate the sensitivity of cervical cancer screening with NNA ranges from 90% to 99%; most pooled estimates fall in the range of 97-99%. An economic analysis using the APL-based "Cervical Cancer Screen" computer model developed by Eddy (Eddy DM. Screening for cervical cancer. Ann Intern Med 1990;113:214-26) and these effectiveness estimates as inputs showed that NNA analysis involves an accepted level of resource expenditure (approximately $40,000 per life year saved) when added to unassisted screening on a triennial basis.Conclusion: The sensitivity of cervical cancer screening with NNA rescreening using the Papnet system yields sensitivities in excess of 90% and approaching 99%.

A new payment system for outpatient services? The implications for radiology

Congress is now contemplating the most significant change in outpatient payment methodology in Medicare's 31-year history. It may approve a proposal by the Health Care Financing Administration (HCFA) to establish a Medicare prospective payment system for hospital outpatient departments. In March 1955, five years after a Congressional directive to develop a new outpatient payment system, HCFA delivered its proposal recommending use of the ambulatory patient groups (APG) classification system for determining payment of hospital outpatient services. The APG system, which uses outpatient procedures as its primary variable, divides all such procedures into one of three categories: 1) significant procedures or therapies (including therapeutic and other significant radiological procedures); 2) ancillary test and procedures (including 11 radiology ancillary service APGs); or 3) medical visits. Outpatients can be assigned to one or more of the 290 APGs, each comprising a number of clinically and resource intensity-similar procedures, medical visits or ancillary tests. Any new payment methodology for outpatient procedures would broadly impact the radiology community. How radiology providers will fare under the system being proposed will depend on several issues that have not yet been resolved, such as how the basic unit of payment is defined (e.g., a service, a visit, or an episode of care) and whether payment rates will be adequate to compensate for the costs of providing services. One key issue will be whether contrast media and radiopharmaceuticals will continue to be paid as pass-through costs, giving providers the flexibility to choose the specific agent that is most appropriate for their patients.

Measurement of short-term, intermediate, and long-term outcomes of treating hypertension

Hypertension is widely treated by primary care physicians as well as by cardiologists and other specialists. Clinical progress is often monitored by blood pressure measurements and other routine evaluations, but more sophisticated approaches may be required to learn whether treatment is effectively protecting the heart, kidneys, and other susceptible areas. Outcome measures therefore involve quantification of short-term, intermediate and long-term clinical observations; and, in addition, assessment of overall effectiveness must take into account economic factors and the levels of satisfaction perceived by patients, physicians, and health plans.

MRI efficacy and effectiveness research: who needs it and who pays for it?

Health care reform has made quality efficacy research in MRI important to an increasing number of audiences. Historically, the deficit of quality outcomes research in MRI was due to difficulties in study design, lack of funding, disincentives for researches and funding sources, and poor coordination. These issues would be best addressed by the formation of an MRI implementation group that would coordinate funding, planning, and dissemination of the outcomes research efforts.

Effect of renal impairment on disposition of pentopril and its active metabolite

Disposition of pentopril was studied in 15 male volunteers with varying renal functions. Mild to moderate compromise in renal function did not demonstrate any appreciable changes in plasma concentration of pentopril, the prodrug ester of the active angiotensin-converting enzyme (ACE) inhibitor CGS 13934. This is consistent with the known elimination pattern for pentopril, which is eliminated primarily by hydrolysis to the active inhibitor. In contrast, the plasma concentration of the active ACE inhibitor was sensitive to moderate changes in renal function. Because of the reciprocal relationship of AUC and clearance, AUC did not change to any appreciable extent until creatinine clearance (CLCR) dropped to about 50 ml/min. Below 50 ml/min of CLCR, AUC and half-life increased sharply with reduced kidney function. Because of the significant contribution of the renal secretion process to total renal elimination of both pentopril and the active metabolite, prediction of renal clearance from CLCR was poor at relatively normal kidney function (CLCR greater than 80 ml/min). However, renal secretory clearances for both pentopril and metabolite were well correlated to p-aminohippuric acid clearance. In patients with moderately compromised renal function (glomerular filtration rate less than 40 ml/min), tubular secretion rate of creatinine approaches its glomerular filtration rate and hence CLCR could be used as a predictor of renal clearance and other disposition parameters. Plasma ACE activity also demonstrated prolonged inhibition with decreased renal function. Based on the prolonged blockade of plasma ACE activity, some correction in dose or dosing interval is anticipated in patients with moderately compromised renal function (CLCR less than 50 ml/min).

Pharmacokinetics of pentopril in the elderly

1 The pharmacokinetics of pentopril in elderly subjects aged 70 to 75 years were compared with those of healthy young subjects aged 22 to 26 years. 2 There were no appreciable differences between the two groups in any of the pharmacokinetic parameters for pentopril derived from its plasma data (Cmax, tmax, AUC and t1/2). 3 In contrast, the active metabolite CGS 13934 exhibited an increase in mean values of AUC by 56% in elderly compared to young. However, the difference was not statistically significant (0.1 greater than P greater than 0.05). The variability was, however, significantly higher (P less than 0.05) in the elderly group compared with young. The peak time for metabolite was also significantly delayed in elderly (3.9 vs 2.5 h). The mean half-life for metabolite however, was comparable for the two groups (3.6 vs 3.9 h). 4 Urinary analysis showed a significant decrease in renal clearance (CLR) with age for both pentopril (107 vs 203 ml min-1) and its active metabolite (116 vs 205 ml min-1). 5 Pharmacodynamic measurements of the renin-angiotensin system, in general, demonstrated a drug effect at 2 h with recovery almost to the basal value at 24 h except for plasma ACE activity at 24 h in the elderly. 6 Because of large variability and an increase in the mean AUC of active metabolite in elderly, greater caution may be necessary for dose selection in this group. However, no substantial difference in extent of drug accumulation is anticipated in elderly compared with young people based on the similarity in t1/2 values.