Reflex strategy to ensure accurate total testosterone results from consumer initiated, self-collected capillary samples

BACKGROUND

Self-collected capillary samples are convenient for direct access testing (DAT), but exogenous testosterone use may cause falsely elevated total testosterone (TT) results. We designed a quality assurance workflow to differentiate between accurate or erroneous supraphysiological TT concentrations.

METHODS

Clinical samples with TT > 1500 ng/dL were reflexed to luteinizing hormone (LH) and follicle stimulating hormone (FSH) and screened for exogenous testosterone use. Samples (n = 120) with normal TT were reflexed to LH/FSH as a control.

RESULTS

A total of 8572 TT samples were evaluated, of which 533 (6.2 %) had TT > 1500 ng/dL and were reflexed. Of these, 441 (82.7 %) had significantly decreased LH/FSH (<0.85/<0.7mIU/mL, respectively), 72 (13.5 %) had normal or borderline normal LH/FSH, and 20 (3.8 %) had insufficient plasma volume. In patients with TT > 1500 ng/dL, injectable exogenous testosterone use was most commonly accompanied by significantly decreased LH/FSH, while topical testosterone use was most commonly accompanied by detectable LH/FSH. Control samples were almost all (99.2 %) within or above the LH/FSH reference intervals. Unique patients ordered 351 TT tests where at least one TT result was > 1500 ng/dL. Based on TT and LH/FSH results, we hypothesized that patients were intermittently or consistently overusing exogenous testosterone, resolved elevated TT with recollection, or repeatedly contaminated their sample.

CONCLUSION

Self-collected capillary specimens are acceptable for TT testing. A quality assurance reflex to LH/FSH can determine the validity of supraphysiological TT results in a consumer initiated/DAT population.

Development and validation of an LC-MSMS method to quantify creatinine from dried blood spots

Introduction

Screening for chronic kidney disease relies on accurate and precise creatinine measurements. Traditionally, creatinine is measured in serum or plasma using high-throughput chemistry analyzers. However, dried blood spots (DBS) can also be utilized to improve testing access.

Methods

Samples were obtained from a 6 mm DBS punch, which was reconstituted in water before undergoing an acetonitrile crash. The resulting supernatant was diluted using an 80:20 acetonitrile: water before injection. Creatinine was identified using an isocratic gradient, and detected using an API 4000 triple quadrupole mass analyzer. Quantification relied on matrix-matched calibrators, with values harmonized to the Roche Cobas enzymatic assay. Validation studies assessing method performance included precision, linearity, accuracy, method comparison, stability, interference, and matrix effects.

Results

The LC-MSMS assay was linear from 0.3 to 20 mg/dL (y = 1.02x-0.11; R2 = 0.996). Precision ranged from 5.2 to 8.1 % using matrix-matched controls (n = 4) that spanned the analytical measurement range. LC-MSMS results corresponded to the enzymatic assay (Roche) with a fitted line equation of y = 0.956x-0.07 (R2 = 0.995; n = 173). The Siemens and Roche enzymatic assays demonstrated higher accuracy in correlating to the DBS creatinine concentration (n = 40 paired venous/DBS collections) compared to the Beckman Jaffe assay (-2.5 % and -0.8 % versus -6.3 % and -4.1 %, respectively) or the iSTAT (-28.4 % and -27.1 %, respectively). Accuracy was unaffected by hematocrit, blood spot volume, excess IgG or IgA, or hypertriglyceridemia. No matrix effects were observed, and both extraction and processing efficiency were robust.Ambient stability extended to at least 10 days, and exposure to extreme temperature did not affect the creatinine results.

Conclusion

We successfully developed an accurate and precise LC-MSMS method for quantifying creatinine in DBS.

Evaluation of Pre-Analytical Variables for Human Papillomavirus Primary Screening from Self-Collected Vaginal Swabs

Human papillomavirus (HPV) primary screening is an effective approach to assessing cervical cancer risk. Self-collected vaginal swabs can expand testing access, but the data defining analytical performance criteria necessary for adoption of self-collected specimens are limited, especially for those occurring outside the clinic, where the swab remains dry during transport. Here, we evaluated the performance of self-collected vaginal swabs for HPV detection using the Cobas 6800. There was insignificant variability between swabs self-collected by the same individual (n = 15 participants collecting 5 swabs per participant), measured by amplification of HPV and human β-globin control DNA. Comparison of self-collected vaginal swab and provider-collected cervical samples (n = 144 pairs) proved highly concordant for HPV detection (total agreement = 90.3%; positive percentage agreement = 84.2%). There was no relationship between the number of dry storage days and amplification of HPV (n = 68; range, 4 to 41 days). Exposure of self-collected dry swabs to extreme summer and winter temperatures did not affect testing outcomes. A second internal control (RNase P) demonstrated that lack of amplification for β-globin from self-collected specimens was consistent with poor, but not absent, cellularity. These data suggest that self-collected vaginal samples enable accurate clinical HPV testing, and that extended ambient dry storage or exposure to extreme temperatures does not influence HPV detection. Furthermore, lack of β-globin amplification in HPV-negative samples accurately identified participants who required recollection.