Advances and challenges in the measurement of 1,25-dihydroxyvitamin D: a comprehensive review.

Vitamin D has received significant attention from clinical societies, researchers, and the general population in recent years. While 25-hydroxyvitamin D (25(OH)D) is the most commonly-used biomarker of vitamin D status, 1α,25-dihydroxyvitamin D (1,25(OH)2D), its bioactive form, plays a critical role in regulating calcium and phosphorus homeostasis and is also involved in the immune system and cellular differentiation. Consequently, accurate measurements of 1,25(OH)2D can aid in the differential diagnosis of calcium-related disorders such as hypocalcemia in vitamin D-dependent rickets and hypercalcemia due to inappropriate increase of serum 1,25(OH)2D in granulomatous diseases. However, due to its lipophilicity and very low circulating concentration, the measurement of 1,25(OH)2D is particularly challenging. Over the past several decades, numerous efforts have been made to develop sensitive, specific, and practical laboratory methods for measuring 1,25(OH)2D. Methods using radioreceptor assay, radioimmunoassay, enzyme immunoassay, enzyme-linked immunosorbent assay, automated chemiluminescent immunoassay, and liquid chromatography-tandem mass spectrometry have been described. Each of these methods has unique advantages and limitations, and some are no longer used. Despite the sophisticated methods in use today, substantial variations between methods still exist. A concerted effort toward standardization of 1,25(OH)2D measurement is needed to ensure accurate and reliable results across laboratories and methods.

Predictive Value of Positive Drug Screening Results in an Urban Outpatient Population.

Urine drug testing (UDT) has become an essential component in the management of patients prescribed opioid analgesics for the treatment of chronic non-malignant pain. Several laboratory methods are available to monitor adherence with the pharmacological regimen and abstinence from illicit or unauthorized medications. Immunochemical screening methods are rapid and economical, but they have limitations, including lack of specificity, and confirmatory methods are often necessary to verify presumptive positive results. We analyzed the results of confirmatory assays in an outpatient setting to determine the predictive value of presumptive positive urine drug screen results using an automated immunoassay for eight common drugs or drug classes. Positive predictive values (PPVs), in descending order, were as follows: cannabinoids (100%), cocaine (100%), opiates (86.8%), benzodiazepines (74.6%), oxycodone (67.6%), methadone (44.1%) and amphetamines (9.3%). The number of positive barbiturate results was too small to be included in the statistical analysis.

Sensitivity of an opiate immunoassay for detecting hydrocodone and hydromorphone in urine from a clinical population: analysis of subthreshold results.

Urine drug testing (UDT) is an emerging standard of care in the evaluation and treatment of chronic non-cancer pain patients with opioid analgesics. UDT may be used both to verify adherence with the opioid analgesic regimen and to monitor abstinence from non-prescribed or illicit controlled substances. In the former scenario, it is vital to determine whether the drug is present in the urine, even at low concentrations, because failure to detect the drug may lead to accusations of opioid abuse or diversion. Opiate immunoassays typically are developed to detect morphine and are most sensitive to morphine and codeine. Although many opiate immunoassays also detect hydrocodone (HC) and/or hydromorphone (HM), sensitivities for these analytes are often much lower, increasing the possibility of negative screening results when the drug is present in the urine. We selected 112 urine specimens from patients who had been prescribed HC or hydromorphone but were presumptive negative by the Roche Online DAT Opiate II™ urine drug screening assay, which is calibrated to 300 ng/mL morphine. Using a GC/MS confirmatory method with a detection limit of 50 ng/mL both for HC and for HM, one or both of these opiates were detected in 81 (72.3%) of the urine specimens. Examination of the raw data from these presumptive negative opiate screens revealed that, in many cases, the turbidity signal was greater than the signal obtained for the negative control, but less than the signal for the 300 ng/mL (morphine) threshold calibrator. A receiver operating characteristic curve generated for the reciprocal of the ratio of turbidity measurements in the patient specimens and negative (drug-free) controls, against the presence or absence of HC and/or HM by confirmatory analyses, produced an area under the curve of 0.910. We conclude that this opiate immunoassay has sufficient sensitivity to detect HC and/or HM in some urine specimens that screen presumptive negative for these commonly prescribed opiates at the established threshold.

Diagnostic value of imprint cytology during image-guided core biopsy in improving breast health care.

The aim of this study was to investigate the accuracy of imprint cytology (IC) of breast core biopsy under ultrasound guidance and to assess the value of a rapid on-site preliminary diagnosis of breast lesions. A total of 437 breast core needle biopsies under ultrasound guidance with touch imprint cytology, histology, and final diagnosis were reviewed. These cases were collected from archived files at our institution. Of 437 core biopsies, IC classified 241 (55%) as benign; 22 (5%) as probably benign; 28 (6%) as probably malignant; 107 (25%) as malignant; and 39 (9%) as inadequate for IC diagnosis. Histological classifications for the 437 cases were: 285 (65%) benign; 132 (30%) malignant; 16 (4%) atypical hyperplasia; and 4 (1%) inadequate specimen. The overall sensitivity and specificity indices of IC were 95% and 96%, respectively, for benign and probably benign lesions vs malignant and probably malignant breast lesions. The overall positive and negative predictive values were 91% and 97%, respectively. The overall accuracy was 95% (379 of 398 cases, excluding specimens inadequate for IC diagnosis). IC of ultrasound-guided core needle biopsy provides a rapid and reliable preliminary diagnosis for breast lesions; it also serves as a means to verify the adequacy of biopsy specimens and to optimize the biopsy procedure. Use of IC may reduce anxiety in patients with benign lesions and expedite the diagnosis and assessment of treatment options in patients with breast cancer.

Urine drug test interpretation: what do physicians know?

OBJECTIVE: To determine the level of urine drug test (UDT) interpretive knowledge of physicians who use these instruments to monitor adherence in their patients on chronic opioid therapy. METHODS: A seven-question instrument consisting of six five-option, single-best-answer multiple choice questions and one yes/no question was completed by 114 physicians (77 who employ UDT and 37 who do not) attending one of three regional opioid education conferences. We calculated frequencies and performed chi2 analyses to examine bivariate associations between UDT utilization and interpretive knowledge. RESULTS: The instrument was completed by 80 percent of eligible respondents. None of the physicians who employ UDT answered all seven questions correctly, and only 30 percent answered more than half correctly. Physicians who employ UDT performed no better on any of the questions than physicians who do not employ UDT. CONCLUSIONS: Physicians who employ UDT to monitor patients receiving chronic opioid therapy are not proficient in test interpretation. This study highlights the need for improved physician education; it is imperative for physicians to work closely with certified laboratory professionals when ordering and interpreting these tests.

False elevation of serum CA-125 level caused by human anti-mouse antibodies.

Discordant results were observed for serum CA-125 (carbohydrate antigen-125) assays in a patient who was monitored for recurrence of ovarian cancer. Serum CA-125 levels in this patient were normal when measured in one laboratory, but >5-times the upper limit of normal (35 U/mL) when measured in another laboratory. Both laboratories used dual antibody heterogeneous immunoassays, but from different manufacturers. Cross-linking heterophilic antibodies were suspected as a cause of the discrepancy, but the interference was not alleviated after 10-fold dilution. Assay of the patient's serum for human anti-mouse antibodies was positive, but only slightly above the reference range. Addition of blocking antibodies eliminated the interference, showing that human anti-mouse antibodies were the cause of the discrepant CA-125 results. These findings indicate that relatively low concentrations of human anti-mouse antibodies can cause significant interference in two-site immunoassays.