Assessment of utility of daily patient results averages as adjunct quality control in a weekday-only satellite chemistry laboratory

ABSTRACT Background: Our department operates a weekday-only (8AM-5PM) satellite laboratory in an infusion center with a menu of 18 chemistry tests on a Roche c501 analyzer. We examined whether daily patient results averages (PRA) in this setting might be useful as a patient-based quality control (PBQC) adjunct to standard daily liquid quality control (LQC) measurements. First, we evaluated the reproducibility (coefficient of variation, CV) of daily PRAs for each analyte, and compared these to CVs of LQC. Second, for select analytes found to have relatively low PRA CVs, we evaluated the extent to which use of daily PRA measurements could improve detection of analytical errors when combined with LQC. Methods: Patient results data for approximately one month (21 weekdays) were obtained from the Sunquest laboratory information system. For calculation of patient results averages (PRA), qualifying results were restricted to those within the reference range for each analyte. PRA and standard deviation (S) of PRA across 21 days was calculated for each analyte. Coefficients of variation for PRA (CV-PRA) were compared to those observed for standard liquid quality control (LQC) measurements (CV-LQC). For those analytes for which CV-PRA was less than CV-LQC, we evaluated the potential advantage of addition of PRA to daily LQC. For each analyte, a presumed PRA shift was determined such that probability of detection (P) was 0.5 when using LQC alone (viz., using high LQC and low LQC measurements), according to criterion that at least one 1-2S deviation from mean was obtained. For this same PRA shift, P = 0.5 for LQC alone was compared to P obtained for LQC + PRA (viz., using high LQC, low LQC, and PRA measurements), according to the same criterion. Results: Across 21 days, the number of results per day per assay ranged from 23 ±4 (uric acid) to 75 ±21 (electrolytes). Qualifying results (results within the reference range) ranged from 70 ± 6 % (LDH) to 99 ± 1 % (Cl). Seven analytes had CV-PRA \u3c CV-LQC (analyte, CV%): albumin, 1.25%; Ca, 0.67%; Cl, 0.62%; CO2, 1.13%; creatinine, 3.44%; K, 1.14%; Na, 0.65%. The remainder did not meet this criterion: ALP, 3.7%; ALT, 5.2%; AST, 5.1%; BUN, 4.6%; glucose, 1.4%; LDH, 2.0%; Mg, 1.4%; P, 2.5%; protein, 0.9%; TBIL, 6.1%; uric acid, 4.3%. Among the seven analytes for which CV-PRA \u3c CV-LQC, probability (P) of shift detection by LQC for circumstances as described in Methods (LQC P = 0.5) was increased substantially by inclusion of PRA (analyte, shift in analyte concentration, P): CO2, ±1.07 mmol/L, 0.97; creatinine, ±0.099 mg/dL, 0.93; albumin, ±0.126 g/dL, 0.85; Ca, ±0.14 mg/dL, 0.80; K, ±0.097 mmol/L, 0.76; Cl, ±1.24 mmol/L, 0.74; Na, ±1.48 mmol/L, 0.68. Conclusions: For 7 analytes, daily PRA demonstrated CVs less than those for LQC. For these analytes, calculations demonstrated that daily PRA can increase probability of detection of small results shifts when used as an adjunct to LQC. Daily PRA is a simple and essentially cost-free form of PBQC that may be useful for certain analytes in part-time laboratory settings

Tumor Doubling Time of Pulmonary Carcinoid Tumors Measured by CT

Introduction: Pulmonary carcinoid tumor (PCT) is a rare neuroendocrine lung cancer that is known clinically to be a slow-growing neoplasm. Few studies have established the true growth rate of these tumors when followed over time by radiography. Therefore, we sought to determine PCT tumor doubling time using longitudinal Computed Tomography (CT) scans. Nodule guidelines may misclassify early PCT nodules with a small diameter as benign if tumor growth is too slow to be appreciable on follow up radiographic scans completed between six months and two years after initial detection. Methods: We performed a retrospective analysis of available CT imaging of all PCTs treated at Thomas Jefferson University Hospital between 2006-2020 where radiographic follow up occurred prior to biopsy or resection. Nodule dimensions were measured manually using Phillips Intellispace PACS or retrieved from radiology reports. Tumor doubling time was calculated for all tumors demonstrating definitive growth (an increase in average diameter ≥ 2 mm) over a follow up interval of at least two years. Results: Fifteen patients had pathologically proven PCT with pre-resection observation times exceeding two years. 12/15 (80%) were typical carcinoids and 3/15 were atypical. 11/12 of the typical PCTs demonstrated definitive growth with a median doubling time of 140 weeks (mean = 161 ± 105 weeks). Discussion: The median doubling time of typical PCT was 141 weeks, or almost three years. It is conceivable that PCTs detected early with small diameter may be mistaken for benign non-growing lesions when followed for less than two years in low-risk patients