Cost-effectiveness of strategies for testing current hepatitis C virus infection.

UNLABELLED: Six strategies for identifying hepatitis C virus (HCV) viremia, involving testing for HCV antibody (HCVAb) followed by a nucleic acid test (NAT) for HCV RNA when the antibody test is positive, are compared. Decision analysis was used to determine mean relative cost per person tested and outcomes of HCV viremia detection. Parameters included proportions of test population with HCVAb and viremia plus specificity, sensitivity, and cost of individual tests. For testing a population with an HCVAb seroprevalence of 3.25%, all strategies when adopting quantitative NAT vary little in cost (range, $29.50-$30.70) and are highly viremia specific (≥0.9997). Four of the strategies using venipuncture blood for HCVAb testing (whether laboratory conducted or employing a rapid, point-of-care assay) and for NAT (whether done by reflex or using separately drawn blood) achieve the highest viremia sensitivities (range, 0.9950-0.9954). Point-of-care HCVAb testing in fingerstick blood followed by NAT in venipuncture blood yields relatively lower viremia sensitivity (0.9301). The strategy that requires returning for NAT is even less viremia sensitive (<0.9000) because of follow-up loss. Strategies adopting qualitative rather than quantitative NAT are slightly cheaper (range, $28.90-$29.99), similarly viremia specific (≥0.9997), but less viremia sensitive (≤0.9456). Viremia sensitivity and specificity remain the same regardless of the proportion of HCVAb-seropositive persons in the cohort being tested. CONCLUSIONS: Strategies involving HCVAb testing in venipuncture blood, whether laboratory conducted or using a point-of-care assay, when followed by quantitative NAT done reflexively or in separately drawn blood, are comparably economical and suitably viremia sensitive. Less cost-effective is point-of-care HCVAb testing in fingerstick blood followed by NAT in venipuncture blood. Least cost-effective is the strategy requiring the tested person to return for NAT.

Comparison of serial Hepatitis C virus detection in samples submitted through serology for reflex confirmation versus samples directly submitted for quantitation.

Using real-time technology, we reliably identified chronic hepatitis C virus (HCV) infection and quantified virus from reflex samples originally submitted for serologic testing. There was no need to process specimens obtained directly for quantitation separately. Whether the initial source is a reflex sample or one obtained directly, a repeat HCV RNA test is needed before starting treatment.

Celiac disease in an urban VA population with iron deficiency: the case against routine duodenal biopsy.

BACKGROUND: Celiac disease is considered an under-recognized cause of iron deficiency. Small intestinal biopsy is proposed to be part of routine evaluation for iron deficiency. AIMS: To determine the prevalence of celiac disease in an urban, mostly male, mostly minority population with iron deficiency. METHODS: Clinical, endoscopic, and pathologic records of veterans who had undergone esophagogastroduodenoscopy (EGD) and duodenal biopsy for iron deficiency at an urban, tertiary care Veterans Affairs Medical Center were reviewed. The yield of positive duodenal biopsies for celiac disease and pre-defined clinically important findings on EGD were calculated. Confounding factors were assessed in multivariate analysis. The main outcome measures were prevalence of celiac disease and prevalence of clinically important findings on upper gastrointestinal endoscopy. RESULTS: The records of 310 veterans were reviewed. Mean age was 63, range 32-91 years old. Most were male (89%) and African-American (73%). Five of 306 small intestinal biopsies were consistent with celiac disease (type 1 lesions), but tissue transglutaminase obtained in four of the patients was normal, making the prevalence of potential celiac disease 0.33% (95% CI: 0.06-1.83%). Fifty of 310 EGDs demonstrated findings that were considered to have a moderate or high probability of producing iron deficiency (16.1, 95% CI: 12.5-20.6%). CONCLUSIONS: The prevalence of celiac disease is low in an urban, predominately male, African-American population with iron deficiency. Routine small intestinal biopsy for celiac disease in similar populations should not be done. EGD remains clinically important.

Laboratory tests of thyroid function: uses and limitations.

Laboratory tests are the most commonly used aids in the diagnosis and monitoring of individuals who have thyroid disease. This article briefly summarizes the common methods of laboratory testing relating to thyroid disease and discusses specific information for individual tests on methods of analysis, their limitations, and situations where caution should be used in interpreting the results of thyroid tests.

Low vitamin B-12 concentrations in patients without anemia: the effect of folic acid fortification of grain.

BACKGROUND: In some patients with vitamin B-12 deficiency mistakenly treated with folic acid, anemia resolved but neurologic complications became worse (masking). Fortification of enriched cereal grains with folic acid has raised concerns that people who consume large quantities of cereal grains, particularly the elderly, may be at increased risk of masking. It is unclear, however, what proportion of people with low vitamin B-12 concentrations do not have anemia and whether the proportion is increasing. OBJECTIVE: We investigated whether fortification has increased the proportion of patients with low vitamin B-12 but without anemia. DESIGN: We reviewed the laboratory results of every patient for whom a vitamin B-12 concentration was measured at the Veterans Affairs Medical Center in Washington, DC, between 1992 and 2000. Those with a low vitamin B-12 concentration (< 258 pmol/L) had their hematocrits and mean cell volumes checked. The proportion without anemia was examined by year before, during, and after folic acid fortification began. RESULTS: There were 1573 subjects with a low vitamin B-12 concentration. The proportion without anemia did not increase significantly from the prefortification period (39.2%) to the period of optional fortification (45.5%) and the postfortification period (37.6%). These findings did not change when the analysis was limited to patients aged > 60 y or when a more conservative definition of low vitamin B-12 (< 150 pmol/L) was used. CONCLUSIONS: Despite evidence that folic acid exposure has increased dramatically since food fortification began, this population showed no evidence of an increase in low vitamin B-12 concentrations without anemia. If confirmed, these results would indicate that food fortification has not caused a major increase in masking of vitamin B-12 deficiency.

Sodium-wasting nephropathy caused by cisplatin in a patient with small-cell lung cancer.

We describe a case of severe hyponatremia following chemotherapy administration in a patient with small-cell lung cancer. There was no evidence of the syndrome of inappropriate antidiuretic hormone (SIADH) secretion. The clinical and laboratory findings were consistent with a sodium-wasting nephropathy complicating cisplatin administration. There are few well-documented reports of cisplatin-associated hyponatremia in the medical literature. We have summarized the relevant literature and attempted to define the differential diagnosis of hyponatremia in this setting. Most cases are accounted for by sodium-losing nephropathy of SIADH, but many reported cases contain insufficient data for classification. Appropriate attention to the evaluation of hyponatremia following platinum-based chemotherapy is needed to properly treat these conditions.

Lab Tests Online and consumer understanding of laboratory testing.

Lab Tests Online is a "peer-reviewed, non-commercial, patient-centered" resource where patients and their relatives and caregivers can learn about the tests used to screen for, diagnose, and manage disease. Consumers are becoming increasingly involved in the management of their own health care and increasingly have access to their laboratory results through electronic health records. Research has shown that consumers have difficulty with health literacy in general and with numerical data in particular. The Lab Tests Online global websites are an important step toward helping consumers understand the complexity of the pathology process, the expertise of the people involved and the meaning of the results provided to them and their healthcare professionals.

Cost effectiveness of testing strategies for chronic hepatitis C.

OBJECTIVE: This paper compares nine strategies for determining hepatitis C antibody and viral status. They combine two tests for antibodies (enzyme immunoassays (EIA), recombinant immunoblot assays (RIBA)) and one for viremia (reverse transcription polymerase chain reaction (PCR)). Using optical density to divide EIA results into three categories (high positive, low positive, negative) was also considered. METHODS: Decision analysis compared strategies on cost as well as sensitivity and specificity with regard to antibody and viral status. Parameters in the decision tree included antibody prevalence, proportion viremic, sensitivity, specificity, and cost of individual tests. RESULTS: The two best strategies are EIA followed by PCR (EIA-->PCR); and EIA with three levels of optical density (EIA-OD), followed by RIBA for EIA-OD low positives, and then PCR for all positives (EIA-OD-->RIBA-->PCR). EIA-->PCR has equal viral sensitivity, slightly lower cost, slightly higher antibody sensitivity, but lower antibody specificity compared to EIA-OD-->RIBA-->PCR. The cost per false antibody positive avoided using EIA-OD-->RIBA-->PCR rather than EIA-->PCR is $36 when prevalence is 5%, and $193 when prevalence is 50%. Using EIA-OD-->RIBA-->PCR rather than EIA-->PCR results in 112 false antibody positives avoided for every true antibody positive missed when prevalence is 5%; this ratio is 18:1 when prevalence is 25%; and 6:1 when prevalence is 50%. CONCLUSIONS: EIA-OD-->RIBA-->PCR is the best choice when prevalence in the tested group is below 20%. As prevalence increases, the choice of EIA-OD-->RIBA-->PCR versus EIA-->PCR will depend on the relative importance of avoiding false antibody positives versus missing true antibody positives. Our analysis makes explicit the magnitude of this trade-off.