The transferrin/log(ferritin) ratio: a new tool for the diagnosis of iron deficiency anemia.

BACKGROUND: Serum ferritin is the best single laboratory test to diagnose iron deficiency anemia (IDA). Ferritin levels <20 µg/L are highly specific for IDA, and ferritin levels >100 µg/L usually exclude IDA. However, ferritin concentrations between 20 and 100 µg/L are often inconclusive. The objective of this study was to improve the diagnosis of IDA when ferritin levels are inconclusive. METHODS: We evaluated the predictive performance of classic (ferritin, mean corpuscular volume, transferrin and serum iron) and modern [reticulocyte hemoglobin content, serum transferrin receptor and soluble transferrin receptor (sTfR)/log(ferr)] iron status parameters to diagnose IDA in 2084 anemic, non-hospitalized patients. The results were validated in an independent cohort of 274 anemic patients. RESULTS: In our study population, 29% (595 patients) of the patients had a ferritin level between 20 and 100 µg/L, hampering diagnosis of IDA. None of the classic or modern parameters was capable of completely separating the IDA population from the non-IDA population. However, using a new parameter, the transferrin/log(ferritin) ratio, the IDA and non-IDA populations can be completely separated. At a cut-off value of 1.70, the transferrin/log(ferritin) ratio indicates IDA in 29% of the patients with inconclusive ferritin levels. CONCLUSIONS: The transferrin/log(ferritin) ratio is a practical new tool that improves diagnosis of iron deficiency when ferritin levels are inconclusive.

Screening for gastrointestinal malignancy in patients with iron deficiency anemia by general practitioners: an observational study.

BACKGROUND: The prevalence of iron deficiency anemia (IDA) is 2-5% in men and postmenopausal women in the developed world. IDA is commonly caused by chronic gastrointestinal blood loss, and a thorough examination of the gastrointestinal tract must be standard practice. OBJECTIVE: To retrospectively study endoscopic evaluations of patients from general practitioners diagnosed with IDA in a peripheral hospital laboratory in order to determine the cause of IDA and the number of gastrointestinal malignancies. MATERIAL AND METHODS: We retrospectively evaluated all patients with IDA diagnosed in a peripheral hospital laboratory by the general practitioner in the region of our hospital from 1 January 2004 until 31 December 2005. We included women older than 50 and men 18 years and older without a history of IDA in the previous 2 years. RESULTS: In 2 years, 287 patients were newly diagnosed with IDA in our hospital laboratory. Only 90 (31%) patients were endoscopically evaluated within 4 months. Gastrointestinal endoscopy revealed at least one lesion potentially responsible for blood loss in 41 of 90 (46%) patients. The most common lesions identified by gastroduodenal endoscopy were erosive esophagitis, gastritis and duodenitis (14%). Cancer was the most commonly detected lesion in the colon, accounting for 17 of 21 colonic lesions explaining IDA. In total, gastrointestinal malignancy was diagnosed in 2% of screened patients. Factors determining the decision for endoscopic screening were lower hemoglobin level, lower ferritin level and male gender. CONCLUSION: In our retrospective study of patients with IDA, only 31% received any form of endoscopic evaluation. In general practice, IDA is investigated suboptimally, and interventions other than the issuing of guidelines are needed to change practice.

A comparative study of conventional versus new, magnesium-poor Vacutainer® Sodium Citrate blood collection tubes for determination of prothrombin time and INR.

INTRODUCTION: Conventional Vacutainer® Sodium Citrate blood collection tubes contain a relatively high concentration of contaminating magnesium ions, which may result in shortening of the prothrombin time (PT) and the International Normalized Ratio (INR). Recently the manufacturer of Vacutainer® Sodium Citrate tubes introduced new tubes with a magnesium-poor stopper. The magnesium concentration in the new low-Mg tubes is significantly lower than that in the conventional plastic tubes. The purpose of the present study was to compare PT and INR determined in specimens drawn with the new tubes to those drawn with the conventional tubes. MATERIALS AND METHODS: Venous blood specimens were collected from 22 healthy persons and 65 patients treated with vitamin K-antagonists using conventional Vacutainer® Sodium Citrate tubes and new, low-Mg Vacutainer® tubes. PT and INR were determined with four thromboplastin reagents, i.e., three brands of recombinant human tissue factor and one brand of combined rabbit brain reagent. Magnesium concentrations were determined in the citrate plasmas with a colorimetric method. RESULTS: The differences in PT, INR and International Sensitivity Index (ISI) between the two tubes were significant when using three recombinant human thromboplastin reagents, but were not significant when using the rabbit thromboplastin. The PT and INR differences between the tubes correlated with the magnesium concentration differences (P<0.001). The INR bias between the four reagents was greater for specimens drawn with conventional tubes than the INR bias for specimens drawn with the new tubes. CONCLUSION: Agreement of INR between reagents is improved by using magnesium-poor tubes.