Antiretroviral Adherence, Elevated Viral Load, and Drug Resistance Mutations in Human Immunodeficiency Virus-infected Women Initiating Treatment in Pregnancy: A Nested Case-control Study.

BACKGROUND: Elevated viral load (VL) early after antiretroviral therapy (ART) initiation appears frequently in pregnant and postpartum women living with human immunodeficiency virus; however the relative contributions of pre-ART drug resistance mutations (DRMs) vs nonadherence in the etiology of elevated VL are unknown. METHODS: Within a cohort of women initiating ART during pregnancy in Cape Town, South Africa, we compared women with elevated VL after initial suppression (cases, n = 80) incidence-density matched to women who maintained suppression over time (controls, n = 87). Groups were compared on pre-ART DRMs and detection of antiretrovirals in stored plasma. RESULTS: The prevalence of pre-ART DRMs was 10% in cases and 5% in controls (adjusted odds ratio [aOR], 1.53 [95% confidence interval {CI}, .4-5.9]); all mutations were to nonnucleoside reverse transcriptase inhibitors. At the time of elevated VL, 19% of cases had antiretrovirals detected in plasma, compared with 87% of controls who were suppressed at a matched time point (aOR, 131.43 [95% CI, 32.8-527.4]). Based on these findings, we estimate that <10% of all elevated VL in the cohort may be attributable to pre-ART DRMs vs >90% attributable to ART nonadherence. CONCLUSIONS: DRMs account for a small proportion of all elevated VL among women occurring in the 12 months after ART initiation during pregnancy in this setting, with nonadherence appearing to drive most episodes of elevated VL. Alongside the drive for access to more robust antiretroviral agents in resource-limited settings, there is an ongoing need for effective strategies to support ART adherence in this patient population.

Accuracy of Self-Reported HIV Status Among African Men and Transgender Women Who Have Sex with Men Who were Screened for Participation in a Research Study: HPTN 075.

Some HIV-infected individuals in research studies may choose not to disclose knowledge of their HIV status to study staff. We evaluated the accuracy of self-reported HIV status among African men and transgender women who have sex with men and who were screened for a research study. Sixty-seven of 183 HIV-infected participants reported a prior HIV diagnosis. Samples from the remaining 116 participants were tested for antiretroviral (ARV) drugs. Thirty-six of the 116 participants had ARV drugs detected, indicating that they were on antiretroviral treatment; these participants were classified as previously diagnosed based on ARV drug testing. Among participants classified as previously diagnosed, disclosure of a prior HIV diagnosis varied among study sites (p = 0.006) and was more common among those who reported having sex with men only (p = 0.002). ARV drug testing in addition to self-report improves the accuracy for identifying individuals with a prior HIV diagnosis.

Use of Antiretroviral Drug Testing to Assess the Accuracy of Self-reported Data from HIV-Infected People Who Inject Drugs.

We used antiretroviral (ARV) drug testing to evaluate the accuracy of self-reported data for HIV status and antiretroviral treatment (ART) among people who inject drugs enrolled in an HIV prevention trial. ARV drugs were detected in enrollment samples from 72/482 = 14.9% HIV-infected participants (39/52 = 75.0% who reported being on ART; 33/430 = 7.7% who reported not being on ART). Overall, 213/482 = 44.2% participants indicated that they were not aware of their HIV-positive status prior to study entry; of those, 30 had ARV drugs detected at enrollment, including 15 who also had ARV drugs detected at the screening visit. These participants were likely aware of their HIV-positive status at study entry but did not report this to study staff. This study shows that self-reported data on HIV testing history and ART may not be accurate and that ARV drug testing can help identify persons who are aware of their HIV-positive status and are on ART.

Evaluation of a Multidrug Assay for Monitoring Adherence to a Regimen for HIV Preexposure Prophylaxis in a Clinical Study, HIV Prevention Trials Network 073.

Daily oral tenofovir disoproxil fumarate (TDF)-emtricitabine (FTC) is a safe and effective intervention for HIV preexposure prophylaxis (PrEP). We evaluated the performance of a qualitative assay that detects 20 antiretroviral (ARV) drugs (multidrug assay) in assessing recent PrEP exposure (detection limit, 2 to 20 ng/ml). Samples were obtained from 216 Black men who have sex with men (208 HIV-uninfected men and 8 seroconverters) who were enrolled in a study in the United States evaluating the acceptability of TDF-FTC PrEP (165 of the uninfected men and 5 of the seroconverters accepted PrEP). Samples from 163 of the 165 HIV-uninfected men who accepted PrEP and samples from all 8 seroconverters were also tested for tenofovir (TFV) and FTC using a quantitative assay (detection limit for both drugs, 0.31 ng/ml). HIV drug resistance was assessed in seroconverter samples. The multidrug assay detected TFV and/or FTC in 3 (1.4%) of the 208 uninfected men at enrollment, 84 (40.4%) of the 208 uninfected men at the last study visit, and 1 (12.5%) of the 8 seroconverters. No other ARV drugs were detected. The quantitative assay confirmed all positive results from the multidrug assay and detected TFV and/or FTC in 9 additional samples (TFV range, 0.65 to 16.5 ng/ml; FTC range, 0.33 to 14.6 ng/ml). Resistance mutations were detected in 4 of the 8 seroconverter samples. The multidrug assay had 100% sensitivity and specificity for detecting TFV and FTC at drug concentrations consistent with daily PrEP use. The quantitative assay detected TFV and FTC at lower levels, which also might have provided protection against HIV infection.

Multicenter evaluation of the thermo scientific prelude for measurement of immunosuppressant drugs using sample preparation liquid chromatography-tandem mass spectrometry.

Immunosuppressant drugs (ISDs) are commonly prescribed to solid organ transplant patients. Their narrow therapeutic index and potential for toxicity necessitates careful monitoring of blood concentrations. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods are increasingly used for ISD measurement. However, there remain many challenges with this methodology, particularly regarding interassay variability. The Thermo Scientific Prelude is an online extraction/liquid chromatography platform that uses turbulent flow technology coupled with MS/MS. A multicenter evaluation of the Prelude for the measurement of cyclosporine A, tacrolimus, and sirolimus is described. ISDs were measured at each site using standardized protocols. Sample preparation liquid chromatography-MS/MS was performed using the Prelude coupled to a TSQ Vantage. Chromatography was achieved with a Cyclone-P TurboFlow/Accucore C8 column combination using a multisolvent loading and eluting pump system. Mass spectrometry acquisitions were performed in selective reaction monitoring mode and data processed using TraceFinder (version 3.1). Multisite mean imprecision for cyclosporine A ranged from 8.8% (54 mcg/L) to 9.8% (450 mcg/L); for tacrolimus, 4.7% (15.5 mcg/L) to 12.6% (2.5 mcg/L); for sirolimus, 7.4% (19.9 mcg/L) to 16.5% (2.6 mcg/L). Approximately 110 specimens were used for method comparison. For cyclosporine A, mean bias against the multisite mean ranged from -18% to 1%; for tacrolimus, values ranged from -7% to 4%; for sirolimus, values ranged from -4% to 2%. Comparisons of multisite mean Prelude results with routine ISD method results was also performed for cyclosporine A (slope = 0.7878, intercept = 24.16, r = 0.98), tacrolimus (slope = 0.9391, intercept = 0.1017, r = 98), and sirolimus (slope = 0.9618, intercept = 0.1483, r = 0.97). The Prelude ISD method offers acceptable and comparable multisite performance. This study has also highlighted the importance of adopting standardized protocols and LC-MS/MS methods for better comparability between ISD assays.

Nondisclosure of HIV status in a clinical trial setting: antiretroviral drug screening can help distinguish between newly diagnosed and previously diagnosed HIV infection.

In The HIV Prevention Trials Network 061 study, 155 human immunodeficiency virus (HIV)-infected men reported no prior HIV diagnosis; 83 of those men had HIV RNA levels of <1000 copies/mL at enrollment. Antiretroviral drug testing revealed that 65 of the 83 (78.3%) men were on antiretroviral treatment. Antiretroviral drug testing can help distinguish between newly diagnosed and previously diagnosed HIV infection.

Failure to identify HIV-infected individuals in a clinical trial using a single HIV rapid test for screening.

BACKGROUND: In the HIV Prevention Trials Network (HPTN) 061 study, 8 (2.3%) of 348 HIV-infected participants identified as HIV uninfected at study enrollment using a single HIV rapid test for screening were found to be HIV infected after additional testing. OBJECTIVES: To evaluate the performance of different HIV assays for detection of HIV infection in HPTN 061 participants with missed infection and individuals with viral suppression. METHODS: Plasma samples from 8 HPTN 061 participants, 17 elite controllers, and 101 individuals on antiretroviral treatment (ART) were tested for HIV with 3 rapid tests, 2 laboratory-based immunoassays, and a Western blot assay. The HPTN 061 samples were also tested with 2 HIV RNA assays and an antiretroviral drug assay. RESULTS: Of the 8 HPTN 061 participants with missed infection, 1 was an elite controller, 1 was taking ART, 2 were missed because of testing or clerical errors, 1 had recent HIV infection (identified using a multi-assay algorithm), and 3 had acute HIV infection. Two (1.7%) of 118 individuals with viral suppression (both taking ART) had at least 1 false-negative test. CONCLUSIONS: In clinical trials, HIV infections can be missed for a variety of reasons. Using more than one assay to screen for HIV infection may reduce the number of missed infections.

Alternative calibration strategies for the clinical laboratory: application to nortriptyline therapeutic drug monitoring.

BACKGROUND: The addition of a calibration curve with every run is both time-consuming and expensive for clinical mass spectrometry assays. We present alternative calibration strategies that eliminate the need for a calibration curve except as required by laboratory regulations. METHODS: We measured serum nortriptyline concentrations prospectively in 68 patients on 16 days over a 2-month period using a method employing calibration schemes that relied on the measurement of the response ratio (RR) corrected by the response factor (RF), i.e., a measurement of the RR for an equimolar mixture of the analyte and internal standard. Measurements were taken with contemporaneous RF (cRF) measurements as well as sporadic RF (sRF) measurements. The measurements with these alternative calibration schemes were compared against the clinical results obtained by interpolation on a calibration curve, and those differences were evaluated for analytical and clinical significance. RESULTS: The differences between the values measured by cRF and sRF calibration and interpolation on a calibration curve were not significant (P = 0.088 and P = 0.091, respectively). Both the cRF- and sRF-based calibration results demonstrated a low mean bias against the calibration curve interpolations of 3.69% (95% CI, -15.8% to 23.2%) and 3.11% (95% CI, -16.4% to 22.6%), respectively. When these results were classified as subtherapeutic, therapeutic, or supratherapeutic, there was categorical agreement in 95.6% of the cRF calibration results and 94.1% of the sRF results. CONCLUSIONS: cRF and sRF calibration in a clinically validated liquid chromatography-tandem mass spectrometry assay yields results that are analytically and clinically commensurate to those produced by interpolation with a calibration curve.

Population-level analysis of natural control of HIV infection in Zambia and South Africa: HPTN 071 (PopART).

INTRODUCTION: HIV controllers have low viral loads (VL) without antiretroviral treatment (ART). We evaluated viraemic control in a community-randomized trial conducted in Zambia and South Africa that evaluated the impact of a combination prevention intervention on HIV incidence (HPTN 071 [PopART]; 2013-2018). METHODS: VL and antiretroviral (ARV) drug testing were performed using plasma samples collected 2 years after enrolment for 4072 participants who were HIV positive at the start of the study intervention. ARV drug use was assessed using a qualitative laboratory assay that detects 22 ARV drugs in five drug classes. Participants were classified as non-controllers if they had a VL ≥2000 copies/ml with no ARV drugs detected at this visit. Additional VL and ARV drug testing was performed at a second annual study visit to confirm controller status. Participants were classified as controllers if they had VLs <2000 with no ARV drugs detected at both visits. Non-controllers who had ARV drugs detected at either visit were excluded from the analysis to minimize potential confounders associated with ARV drug access and uptake. RESULTS: The final cohort included 126 viraemic controllers and 766 non-controllers who had no ARV drugs detected. The prevalence of controllers among the 4072 persons assessed was 3.1% (95% confidence interval [CI]: 2.6%, 3.6%). This should be considered a minimum estimate, since high rates of ARV drug use in the parent study limited the ability to identify controllers. Among the 892 participants in the final cohort, controller status was associated with biological sex (female > male, p = 0.027). There was no significant association between controller status and age, study country or herpes simplex virus type 2 (HSV-2) status at study enrolment. CONCLUSIONS: To our knowledge, this report presents the first large-scale, population-level study evaluating the prevalence of viraemic control and associated factors in Africa. A key advantage of this study was that a biomedical assessment was used to assess ARV drug use (vs. self-reported data). This study identified a large cohort of HIV controllers and non-controllers not taking ARV drugs, providing a unique repository of longitudinal samples for additional research. This cohort may be useful for further studies investigating the mechanisms of virologic control.

Comprehensive profiling of pre-infection antibodies identifies HIV targets associated with viremic control and viral load.

Background: High HIV viral load (VL) is associated with increased transmission risk and faster disease progression. HIV controllers achieve viral suppression without antiretroviral (ARV) treatment. We evaluated viremic control in a community-randomized trial with >48,000 participants. Methods: A massively multiplexed antibody profiling system, VirScan, was used to quantify pre- and post-infection antibody reactivity to HIV peptides in 664 samples from 429 participants (13 controllers, 135 viremic non-controllers, 64 other non-controllers, 217 uninfected persons). Controllers had VLs <2,000 copies/mL with no ARV drugs detected at the first HIV-positive visit and one year later. Viremic non-controllers had VLs 2,000 copies/mL with no ARV drugs detected at the first HIV-positive visit. Other non-controllers had either ARV drugs detected at the first HIV-positive visit (n=47) or VLs <2,000 copies/mL with no ARV drugs detected at only one HIV-positive visit (n=17). Results: We identified pre-infection HIV antibody reactivities that correlated with post-infection VL. Pre-infection reactivity to an epitope in the HR2 domain of gp41 was associated with controller status and lower VL. Pre-infection reactivity to an epitope in the C2 domain of gp120 was associated with non-controller status and higher VL. Different patterns of antibody reactivity were observed over time for these two epitopes. Conclusion: These studies suggest that pre-infection HIV antibodies are associated with controller status and modulation of HIV VL. These findings may inform research on antibody-based interventions for HIV treatment.

Validation of a lateral flow chromatographic immunoassay for the detection of fentanyl in drug samples.

BACKGROUND: Drug overdose deaths remain the primary cause of unintentional injuries in the United States. We examined the validity of a fentanyl test strip (FTS) in detecting fentanyl and its related analogs in water-based illicit drug solutions. METHODS: Illicit drugs obtained from law enforcement (N = 343) were tested using a lateral flow chromatographic immunoassay FTS (BTNX Rapid Response) and Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS) at a clinical chemistry laboratory in Baltimore, Maryland. RESULTS: The FTS assay detected fentanyl at 200 ng/ml in water, and 13 additional fentanyl analogs, but failed to detect carfentanil and furanyl fentanyl at or below 1000 ng/ml. Overall sensitivity and specificity for detecting fentanyls was 98.5 % and 89.2 %; and the false negative and positive rate was 1.5 % and 10.9 %. False negatives (n = 2) occurred in fentanyl and a fentanyl precursor. False positives (n = 23) occurred in the presence of other illicit drugs and compounds (56.5 %) or when fentanyls were present below 40 ng/ml (43.5 %). False positive/negative rates remained low when testing cocaine and prescription opioid (PO) samples. CONCLUSIONS: FTS is a valid drug checking tool, however, rapid immunoassays and other drug checking instruments that can detect a wider range of fentanyl analogs including carfentanil need to be prioritized to minimize accidental exposure to the full spectrum of fentanyls.

HIV drug resistance in a community-randomized trial of universal testing and treatment: HPTN 071 (PopART).

INTRODUCTION: Universal HIV testing and treatment (UTT) has individual and public health benefits. HPTN 071 (PopART), a community-randomized trial in Zambia and South Africa, demonstrated that UTT decreased HIV incidence. This endpoint was assessed in a cohort of >48,000 randomly selected adults in the study communities. We evaluated the impact of UTT on HIV drug resistance in this cohort and compared other resistance-related outcomes in participants with recent versus non-recent HIV infection. METHODS: Two years after the start of HPTN 071 (2016-2017), 6259 participants were HIV positive and 1902 were viremic (viral load >400 copies/ml). HIV genotyping and antiretroviral (ARV) drug testing were performed for viremic participants in three groups: seroconverters (infected <1 year), non-seroconverters (infected >1 year, random subset) and participants with unknown duration of infection (random subset). A two-stage cluster-based approach was used to assess the impact of the study intervention on drug resistance. Treatment failure was defined as being viremic with ARV drugs detected. Participants were classified as ARV naïve based on self-report and ARV drug testing. RESULTS: Genotyping results were obtained for 758 participants (143 seroconverters; 534 non-seroconverters; and 81 unknown duration of infection). The estimated prevalence of resistance in the study communities was 37% for all viremic persons and 11% for all HIV-positive persons. There was no association between UTT and drug resistance. Resistance was detected in 14.0% of seroconverters and 40.8% of non-seroconverters (non-nucleoside reverse transcriptase inhibitor resistance: 14.0% and 39.9%; nucleoside/nucleotide reverse transcriptase inhibitor resistance: 0.7% and 15.5%; protease inhibitor resistance: 0% and 1.9%; multi-class resistance: 0.7% and 16.1%, respectively). ARV drugs were detected in 2/139 (1.4%) of seroconverters and 94/534 (17.6%) of non-seroconverters tested. These participants were classified as failing ART; 88 (93.6%) of the non-seroconverters failing ART had resistance. Mutations used for surveillance of transmitted drug resistance were detected in 10.5% of seroconverters and 15.1% of non-seroconverters who were ARV naive. CONCLUSIONS: UTT was not associated with an increase in drug resistance in this cohort. Higher rates of drug resistance and multi-class resistance were observed in non-seroconverters compared to seroconverters.

Antiretroviral Drug Detection in a Community-Randomized Trial of Universal HIV Testing and Treatment: HPTN 071 (PopART).

Background: Antiretroviral therapy (ART) reduces human immunodeficiency virus (HIV) transmission risk. The primary aim of this study was to evaluate ART uptake in a trial in Zambia and South Africa that implemented a community-wide universal testing and treatment package to reduce HIV incidence. Methods: Study communities were randomized to 3 arms: A, combination-prevention intervention with universal ART; B, combination-prevention intervention with ART according to local guidelines; and C, standard of care. Samples were collected from people with HIV (PWH) during a survey visit conducted 2 years after study implementation: these samples were tested for 22 antiretroviral (ARV) drugs. Antiretroviral therapy uptake was defined as detection of ≥1 ARV drug. Resistance was evaluated in 612 randomly selected viremic participants. A 2-stage, cluster-based approach was used to assess the impact of the study intervention on ART uptake. Results: Antiretroviral drugs were detected in 4419 of 6207 (71%) samples (Arm A, 73%; Arm B, 70%; Arm C, 60%); 4140 (94%) of samples with ARV drugs had viral loads <400 copies/mL. Drug resistance was observed in 237 of 612 (39%) viremic participants (95 of 102 [93%] with ARV drugs; 142 of 510 [28%] without drugs). Antiretroviral therapy uptake was associated with older age, female sex, enrollment year, seroconverter status, and self-reported ART (all P < .001). The adjusted risk ratio for ART uptake was similar for Arm A versus C (1.21; 95% confidence interval [CI], .94-1.54; P = .12) and Arm B versus C (1.14; 95% CI, .89-1.46; P = .26). Conclusions: At the 2-year survey, 71% of PWH were on ART and 94% of those participants were virally suppressed. Universal testing and treatment was not significantly associated with increased ART uptake in this cohort.

Prolonged control of replication-competent dual- tropic human immunodeficiency virus-1 following cessation of highly active antiretroviral therapy.

BACKGROUND: While initiation of highly active antiretroviral therapy (HAART) during primary HIV-1 infection occasionally results in transient control of viral replication after treatment interruption, the vast majority of patients eventually experience a rebound in plasma viremia. RESULTS: Here we report a case of a patient who was started on HAART during symptomatic primary infection and who has subsequently maintained viral loads of < 50 copies/mL for more than nine years after the cessation of treatment. This patient had a high baseline viral load and has maintained a relatively high frequency of latently infected CD4(+) T cells. In addition, he does not have any known protective HLA alleles. Thus it is unlikely that he was destined to become a natural elite controller or suppressor. The mechanism of control of viral replication is unclear; he is infected with a CCR5/CXCR4 dual-tropic virus that is fully replication-competent in vitro. In addition, his spouse, who transmitted the virus to him, developed AIDS. The patient's CD4(+) T cells are fully susceptible to HIV-1 infection, and he has low titers of neutralizing antibodies to heterologous and autologous HIV-1 isolates. Furthermore, his CD8(+) T cells do not have potent HIV suppressive activity. CONCLUSION: This report suggests that some patients may be capable of controlling pathogenic HIV-1 isolates for extended periods of time after the cessation of HAART through a mechanism that is distinct from the potent cytotoxic T lymphocyte (CTL) mediated suppression that has been reported in many elite suppressors.

Uptake of antiretroviral treatment and viral suppression among men who have sex with men and transgender women in sub-Saharan Africa in an observational cohort study: HPTN 075.

OBJECTIVES: HPTN 075 enrolled men who have sex with men (MSM) and transgender women (TGW) in sub-Saharan Africa. Persons in HIV care or on antiretroviral treatment (ART) were not eligible to enroll. We evaluated antiretroviral (ARV) drug use, viral suppression, and drug resistance in this cohort over a 12-month follow-up period. METHODS: Assessments included 64 participants with HIV (39 MSM, 24 TGW, and one gender not specified). ARV drugs were detected using a qualitative assay. Viral load (VL) and drug resistance testing were performed using commercial assays. RESULTS: Over 12 months, the proportion of participants using ARV drugs increased from 28.1% to 59.4% and the proportion with VLs <400 copies/mL increased from 21.9% to 57.8%. The rate of ART failure (detection of drugs without viral suppression) was similar at screening and 12 months (12.0% and 11.1%, respectively) and was similar among MSM and TGW. Two participants developed HIV drug resistance during follow-up. CONCLUSIONS: Over 12 months, ARV drug use in the cohort more than doubled and viral suppression increased nearly threefold without a significant increase in ART failure or drug resistance. These results suggest that ART can be successfully scaled up for HIV prevention and treatment in this high-risk population.

Evaluation of multi-assay algorithms for identifying individuals with recent HIV infection: HPTN 071 (PopART).

BACKGROUND: Assays and multi-assay algorithms (MAAs) have been developed for population-level cross-sectional HIV incidence estimation. These algorithms use a combination of serologic and/or non-serologic biomarkers to assess the duration of infection. We evaluated the performance of four MAAs for individual-level recency assessments. METHODS: Samples were obtained from 220 seroconverters (infected <1 year) and 4,396 non-seroconverters (infected >1 year) enrolled in an HIV prevention trial (HPTN 071 [PopART]); 28.6% of the seroconverters and 73.4% of the non-seroconverters had HIV viral loads ≤400 copies/mL. Samples were tested with two laboratory-based assays (LAg-Avidity, JHU BioRad-Avidity) and a point-of-care assay (rapid LAg). The four MAAs included different combinations of these assays and HIV viral load. Seroconverters on antiretroviral treatment (ART) were identified using a qualitative multi-drug assay. RESULTS: The MAAs identified between 54 and 100 (25% to 46%) of the seroconverters as recently-infected. The false recent rate of the MAAs for infections >2 years duration ranged from 0.2%-1.3%. The MAAs classified different overlapping groups of individuals as recent vs. non-recent. Only 32 (15%) of the 220 seroconverters were classified as recent by all four MAAs. Viral suppression impacted the performance of the two LAg-based assays. LAg-Avidity assay values were also lower for seroconverters who were virally suppressed on ART compared to those with natural viral suppression. CONCLUSIONS: The four MAAs evaluated varied in sensitivity and specificity for identifying persons infected <1 year as recently infected and classified different groups of seroconverters as recently infected. Sensitivity was low for all four MAAs. These performance issues should be considered if these methods are used for individual-level recency assessments.

Analytical performance of 4 automated assays for measurement of cystatin C.

BACKGROUND: We evaluated the analytical performance of 4 cystatin C assays (Siemens N Latex on BNII, Roche Tina-quant on Cobas c501, Genzyme on Cobas c501, and Tosoh ST AIA-PACK on Tosoh AIA-600II) according to guidelines published by the Clinical and Laboratory Standards Institute. METHODS: We evaluated total imprecision, limit of detection, and limit of quantification for each assay using patient serum pools and linearity/recovery using serial dilutions of a patient serum pool with cystatin C-free serum. We compared patients (n = 102) using the Siemens assay as a comparison method. RESULTS: All assays had limits of detection and quantification <0.08 and <0.39 mg/L, respectively. Total CVs were generally higher than the manufacturers' claims for all assays. The Roche assay overrecovered cystatin C, particularly at low concentrations (mean recovery 119%, 142% at 0.587 mg/L). Deming regression equations were y = 1.184x + 0.089, S(y|x) = 0.246 for Genzyme; y = 0.937x + 0.231, S(y|x) = 0.231 for Roche; and y = 1.010x + 0.216, S(y|x) = 0.115 for Tosoh. The Genzyme assay appeared to report higher results than the Siemens assay, which is consistent with a higher reference interval specified by the manufacturer. CONCLUSIONS: Although all assays were acceptable for clinical use, their diagnostic performances were not optimal. Limitations include imprecision greater than claimed, overrecovery for the Roche assay on low concentration samples, and differences in results for patient samples. The latter situation requires assay-specific cystatin C-based glomerular filtration rate prediction equations at least until calibration is standardized using the international cystatin C calibrator now being developed.

Analysis of Busulfan in Plasma by Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS).

Bone marrow transplantation is used to treat particular types of cancers such as lymphoma, leukemia, and multiple myeloma. Appropriate dosing of busulfan during the preparative phase is critical for a successful allograft; if blood concentrations get too high significant liver toxicity can occur, if blood concentrations are too low, then graft-versus-host disease (GVHD) can develop. Busulfan monitoring in blood allows hospitals with the opportunity to provide individualized medicine to patients and improve overall patient outcome. Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS) is an important analytical method for quantification of busulfan in plasma in order to optimize the dose. © 2020 Wiley Periodicals LLC. Basic Protocol: Analysis of busulfan by liquid chromatography/mass spectrometry.

Analysis of Immunosuppressant Drugs in Whole Blood by Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS).

Immunosuppressant medications help suppress the immune system response through inhibition of various checkpoints in the regulatory biochemical pathway. This is useful in prevention of organ rejection in transplantation or in the treatment of autoimmune diseases such as lupus or rheumatoid arthritis. Quantification of immunosuppressive drugs in blood is needed clinically for optimization of treatment and to avoid toxicity or unwanted side effects. Here, we describe a quantitative method to determine the concentration of cyclosprine A, tacrolimus, sirolimus, and everolimus in whole blood. This method has been used for many years clinically to support patient care. © 2020 by John Wiley & Sons, Inc.