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Screening in chronic hepatitis B carriers: a retrospective study in a primary care clinic |
Kung K, Lam A, Li P K |
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Record Status This is a critical abstract of an economic evaluation that meets the criteria for inclusion on NHS EED. Each abstract contains a brief summary of the methods, the results and conclusions followed by a detailed critical assessment on the reliability of the study and the conclusions drawn. Health technology This study examined alpha-fetoprotein (AFP), alanine transaminase (ALT) and ultrasonography (USG) screening programmes. All of which were common practices in the authors' setting to detect cirrhosis or hepatocellular carcinoma (HCC) in chronic hepatitis B virus (HBV) carriers. The cut-off value for abnormal AFP adopted in the study was larger than 7 mg/L.
Economic study type Cost-effectiveness analysis.
Study population The population comprised patients with chronic hepatitis B with a positive hepatitis B surface antigen (HbsAg) for 6 months. All patients were hepatitis Be antigen (HBeAg) negative for hepatitis C. All of the patients were either referred to the family medicine clinic in the Prince of Wales Hospital from the hepatology clinic of the same hospital, or were identified during follow-up for other diseases. The exclusion criteria were patients who had defaulted for any intervention/FU, those who were HBV carriers but not followed up at the authors' clinic for hepatitis, those who were first seen during the 3-month inclusion time period, and patients who required more regular follow-up or liver function testing because of other coexisting diseases.
Setting The study setting was primary care. The economic study was carried out in the family medicine clinic, Prince of Wales Hospital, Shatin, Hong Kong.
Dates to which data relate The effectiveness evidence was retrospectively collected from 1999 to October 2003. The authors did not report the date to which resource use related. The price year was not reported, but it appears to have been given in another source (Prince of Wales Hospital 2003, see 'Other Publications of Related Interest' below for bibliographic details).
Source of effectiveness data The effectiveness data were derived from a single study.
Link between effectiveness and cost data The costing was carried out retrospectively on the same study sample as that used in the effectiveness analysis.
Study sample The patients included in the study were selected from those who had attended the clinic in the Prince of Wales Hospital between 1st July 2003 and 3rd October 2003. Of 351 patients who attended the clinic during this period, 69 were either defaulters, not attending the clinic for follow-up of their hepatitis status, had co-morbidities, or were seen as a new case during this period. The remaining 282 patients were included in the study. Power calculations to determine the sample size were not reported. The authors provided neither the evidence that the study sample was representative of the study population, nor the baseline characteristics of the patients.
Study design This was a diagnostic accuracy study that was conducted in a single centre. Every patient who was entered into the study received both tests.
Analysis of effectiveness The primary health outcomes used in the clinical study were:
the follow-up frequencies,
the intervention frequencies (AFP, ALT, liver USG), and
the sensitivity, specificity and predictive values of AFP and ALT in detecting cirrhosis.
The diagnosis of cirrhosis was based on USG findings (the reference test).
Effectiveness results The mean frequency of follow-up consultation was once every 7 months (standard deviation, SD=4.0; range: 1 - 14).
The mean frequency of AFP was once every 12 months (SD=6.0; range: 2 - 36).
The mean frequency of ALT was once every 11 months (SD=5.6; range: 1 - 29).
The mean frequency of USG was once every 22 months (SD=10.8; range: 6 - 60).
There were no significant differences, (p=0.38), in follow-up frequencies in those with and without cirrhosis. There were significant differences between the frequencies of the three screening modalities and the presence or absence of cirrhosis, (AFP, p=0.0076; ALT, p=0.024; USG, p=0.022).
The sensitivity and specificity of detecting cirrhosis with AFP > 7 mg/L and ALT were both 0.08 and 0.97, respectively. The positive and negative predictive values were 0.20 and 0.92, respectively, with AFP, and 0.22 and 0.90 with ALT.
Clinical conclusions This effectiveness analysis supported the use of USG alone in screening HBV carriers in the primary care setting. Haematological investigations played a minimal role in the monitoring of HBV carriers, especially in those without cirrhosis.
Measure of benefits used in the economic analysis The measures of benefit used were the numbers of occurrences of cirrhosis and HCC detected.
Direct costs The costs included in the economic analysis were those per patient per year for AFP, ALT and liver USG. The cost estimate was derived from the fee schedule for private patients in the Prince of Wales Hospital. The cost boundary adopted was not reported. The costs and the resource quantities were not reported separately. Discounting and a price year were not reported. The costs of running an outpatient department and its associated staff, and time taken off by the patient for tests and psychological burdens, were not considered.
Statistical analysis of costs The costs were not treated stochastically. Hence, no statistical analysis of the costs was carried out.
Indirect Costs No indirect costs were calculated.
Sensitivity analysis No sensitivity analysis was carried out.
Estimated benefits used in the economic analysis All five new occurrences of cirrhosis were detected by USG over a 4-year period. The 14 cases with raised ALT and AFP had normal ultrasound findings. No HCC were detected.
Cost results The costs per patient per year were HK$400 for AFP, HK$200 for ALT and HK$1,000 for liver USG.
The average cost per patient per year for ALT, AFP and USG of HBV carriers without cirrhosis was HK$2,300.
Synthesis of costs and benefits The costs per patient per year per cirrhosis detected were HK$480,000 for the routine test (the average of ALT, AFP and USG), HK$360,000 for yearly USG alone, and HK$590,000 for the recent Asia-Pacific consensus (6-monthly USG and AFP).
Authors' conclusions The use of ultrasonography (USG) alone in screening hepatitis B virus (HBV) carriers in the primary care setting was cost-effective. Haematological investigations played a minimal role in the monitoring of HBV carriers, especially in those without cirrhosis.
CRD COMMENTARY - Selection of comparators The rationale for the choice of the comparators appears to have been clear. The comparators represented common practices in the authors' setting. You should decide whether they are valid comparators in your own setting.
Validity of estimate of measure of effectiveness The analysis was based on a diagnostic accuracy study, which was appropriate for the study question. The method of sample selection was described in detail, and reasons for the reduced sample used in the final analysis were reported. Power calculations were not performed, although it was necessary to examine the appropriateness of the sample size. Therefore, the authors acknowledged that the sample size was somewhat small to detect statistically significant differences in outcomes between the groups. A further drawback of the study was that no confidence intervals were calculated when the sensitivity and specificity of the diagnostic tests were assessed. Therefore, it is difficult to assess the reliability of the test accuracy assessed in the analysis.
Validity of estimate of measure of benefit The summary benefit measures were appropriate as they reflected the impact of the interventions. It seems that the health benefits have not been discounted, although this would have been appropriate given the long time horizon of the model (more than 3 years for some patients, the first consultation dating back to 1999).
Validity of estimate of costs The authors did not state the perspective adopted in the study. The costs included were those of individual tests. The authors also detailed the resource items excluded, although the reasons for their exclusion were not provided. Some limitations were highlighted. First, discounting was not carried out, even though the costs were incurred during more than two years. Second, the unit costs were not given. Third, the costs and the quantities were not reported separately. Fourth, the price year was not reported. Fifth, no conversion rate was reported. Finally, statistical and sensitivity analyses were not carried out. These factors suggest that the cost results should be treated with some caution.
Other issues The authors do not appear to have presented their results selectively. Sensitivity analyses were not performed and the study was carried out in a single location, thus limiting the overall external validity of the study. The interpretation of the results was limited by the small sample size, short reviewing period and lack of new HCC cases. The authors acknowledged that the definition of cirrhosis using USG findings was another drawback because this would inherently bias results towards USG screening. In addition, the authors acknowledged that "population bias may be the key in the marked difference in sensitivity in the study, since most of the cases are stable HBV carriers without complications".
Implications of the study The authors stated that the study supports the use of USG alone in monitoring HBV carriers in the primary care setting. They also suggested that further studies should be undertaken to establish the feasibility of screening by USG alone and to determine different management strategies in different centres.
Bibliographic details Kung K, Lam A, Li P K. Screening in chronic hepatitis B carriers: a retrospective study in a primary care clinic. Hong Kong Practitioner 2004; 26(5): 221-227 Other publications of related interest Gupta S, Bent S, Kohlwes J. Test characteristics of alpha-fetoprotein for detecting hepatocellular carcinoma in patients with hepatitis C: a systematic review and Critical Analysis. Annals of Internal Medicine 2003;139:46-50.
Kang JY, Lee TP, Yap I, et al. Analysis of cost-effectiveness of different strategies for hepatocellular carcinoma screening in hepatitis B virus carriers. Journal of Gastroenterology and Hepatology 1992;17:463-8.
Fee schedule for private patients, 2003. Shatin, Hong Kong: Prince of Wales Hospital; 2003.
Shiu W, Dewar N, Leung N, et al. Hepatocellular carcinoma in Hong Kong: clinical study on 340 cases. Oncology 1990;47:241-5.
Wun YT, Dickinson JA. Alpha-fetoprotein and/or liver ultrasonography for liver cancer screening in patients with chronic hepatitis. In: The Cochrane Library, Issue 2, 2003. Oxford: Update Software.
Indexing Status Subject indexing assigned by CRD MeSH Alanine Transaminase; Carcinoma, Hepatocellular /diagnosis /prevention & Clinical Trials as Topic; Cost-Benefit Analysis; Hepatitis B; Hepatitis B virus; Liver Cirrhosis /diagnosis /prevention & Mass Screening; Sensitivity and Specificity; Ultrasonography; alpha-Fetoproteins; control; control AccessionNumber 22005000088 Date bibliographic record published 31/01/2006 Date abstract record published 31/01/2006 |
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