Evaluation of nine automated high-sensitivity C-reactive protein methods: implications for clinical and epidemiological applications. Part 2

BACKGROUND

C-Reactive protein (CRP) can provide prognostic information about risk of future coronary events in apparently healthy subjects. This application requires higher sensitivity assays than have traditionally been available in the clinical laboratory.

METHODS

Nine high-sensitivity CRP (hs-CRP) methods from Dade Behring, Daiichi, Denka Seiken, Diagnostic Products Corporation, Iatron, Kamiya, Olympus, Roche, and Wako were evaluated for limit of detection, linearity, precision, prozone effect, and comparability with samples from 388 apparently healthy individuals.

RESULTS

All methods had limits of detection that were lower than the manufacturers' claimed limit of quantification except for the Kamiya, Roche, and Wako methods. All methods were linear at 0.3-10 mg/L. The Diagnostic Products Corporation, Kamiya, Olympus, and Wako methods had imprecision (CVs) >10% at 0.15 mg/L. The Iatron, Olympus, and Wako methods demonstrated prozone effects at hs-CRP concentrations of 12, 206, and 117 mg/L, respectively. hs-CRP concentrations demarcating each quartile in a healthy population were method-dependent. Ninety-two to 95% of subjects were classified into the same quartile of hs-CRP established by the Dade Behring method by the Denka Seiken, Diagnostic Products Corporation, Iatron, and Wako methods. In contrast, 68-77% of subjects were classified into the same quartile by the Daiichi, Kamiya, Olympus, and Roche methods. No subject varied by more than one quartile by any method.

CONCLUSIONS

Four of the nine examined hs-CRP methods classified apparently healthy subjects into quartiles of hs-CRP similar to the classifications assigned by the comparison method. Additional standardization efforts are required because an individual patient's results will be interpreted using population-based cutpoints.

Direct measurement of LDL-C in children: performance of two surfactant-based methods in a general pediatric population

OBJECTIVES

Several pediatric advisory groups have recommended selective screening for dyslipidemia in children. Low-density lipoprotein cholesterol (LDL-C) is measured clinically with the Friedewald calculation in fasting samples. Nonfasting measurement of LDL-C would be clinically useful in children.

DESIGN AND METHODS

In the present study, we examine the performance of two surfactant-based direct LDL-C assays in paired samples, fasting and nonfasting, from 100 children.

RESULTS

LDL-C in the fasting state was significantly lower with the Friedewald estimation: 2.43 +/- 0. 61 mmol/L, N-geneous (Genzyme Corp.) direct LDL-C: 2.30 +/- 0.59 mmol/L, and Roche (Roche Diagnostics) direct LDL-C: 2.32 +/- 0.57 mmol/L than with ultracentrifugation-dextran-sulfate-Mg(2+) precipitation (UC-DS): 2.47 +/- 0.64 mmol/L. Moreover, there was increased negative bias using nonfasting samples with N-geneous: 2. 25 +/- 0.56 mmol/L and Roche: 2.26 +/- 0.56 mmol/L compared with fasting UC-DS. Correlation with US-DS was highest for Friedewald (r = 0.974) and fasting N-geneous (r = 0.973), and lowest with nonfasting N-geneous (r = 0.849) and Roche in fasting (r = 0.891) and nonfasting samples (r = 0.747). The sensitivity at LDL-C concentration of 2.85 mmol/L for the two direct methods when either fasting or nonfasting samples were used, was lower than that obtained with Friedewald.

CONCLUSION

Overall, these direct LDL-C assays demonstrated limited utility in screening children but may be useful in the management of lipid disorders.

Prospective analysis of intraoperative frozen needle biopsy of solid renal masses in adults

PURPOSE

We prospectively determined the accuracy of intraoperative needle biopsy of solid renal masses.

MATERIALS AND METHODS

A total of 103 patients diagnosed with a solid renal mass and scheduled for surgery were prospectively evaluated. Radical or partial nephrectomy was performed, and biopsy of the surgical specimen was done twice through the tumor using an 18 gauge biopsy gun. Biopsy specimens of 106 tumors were sent for frozen sectioning, stained with hematoxylin and eosin, and reviewed by 2 independent pathologists blinded to each other and whole tissue specimens. Biopsy results were compared to whole tissue specimens.

RESULTS

Specimens were obtained from 60 radical and 46 partial nephrectomy cases. Malignant neoplasms were present in 91 cases (86%). Overall, 15 cases (14%) were benign, of which 11 were oncocytomas. If lesions 4 cm. or less only were included in analysis, the incidence of benign lesions increased to 22%. Overall accuracy of the 2 pathologists was 76 and 80%. Nondiagnostic rates were 11 and 17%. Both observers incorrectly diagnosed 4 malignant lesions (5%) as benign, and incorrectly diagnosed 3 and 5 benign lesions (21 and 36%), respectively, as malignant. Analysis of values for both observers yielded a sensitivity of 77 and 84%, specificity 60 and 73%, positive predictive value 94 and 96%, and negative predictive value 69 and 73%.

CONCLUSIONS

Overall frozen needle biopsy was accurate in more than 75% of cases and showed an excellent positive predictive value for carcinoma of more than 94%. Unfortunately, there was a large degree of inaccuracy for benign lesions and we do not recommend the routine use of intraoperative frozen needle biopsy to guide surgical decision making.

Effect of high fat and iron levels on the growth and mortality of chickens

Four experiments were conducted with chicks to determine whether the heating of vegetable oil and its contamination with iron might have detrimental effects upon its use in chicken diets. Soybean oil and safflower oil heated at 230 C for 51 hr and linseed oil heated at 240 C for 24 hr gave reduced growth when fed to chickens at 20 percent of the diet. Heating soybean oil at 175 C for 51 hr had no detrimental effect. However, iron at 5000 ppm depressed growth significantly when fed in a low fat diet. The depression was greatly reduced when soybean oil was fed at 10 or 20% of the diet. A different lot of soybean oil was found to cause skin dermatitis and high mortality when fed at 20% of the diet due to its physical contamination on the skin.