In the Interest of Time: Assessing the Role of Resilience Across an Intergenerational Sample of People Living with HIV

BACKGROUND

Biomedical advances have improved the quality of life of people living with HIV (PLWH); however, barriers to optimal well-being remain. A key feature in understanding the lived experiences of PLWH is resilience. The concept of resilience is quite complex in terms of its antecedents and expressions, suggesting the need for more nuanced understandings of how it could be harnessed to better support this population.

METHOD

The concept of resilience was explored in a qualitative study involving 22 PLWH, selectively sampled by era of diagnosis. Through interviews focused on context and experiences of living with HIV, the sample highlighted resilience processes corresponding to Positive reappraisal of life events, Positive reappraisal of self, and Community as resilience.

RESULTS

Participants who have lived with HIV longer more commonly described engaging in psychological processes of resilience, whereas those who were more recently diagnosed reported engaging in more social processes. However, these processes were not mutually exclusive and the ability to perform resilience through community seems to be key to optimizing outcomes, irrespective of era of diagnosis.

CONCLUSION

PLWH are a heterogeneous population where engagement in distinct processes of resilience may have important implications for optimal social and health outcomes. Better understanding of the distinct and diverse pathways through which PLWH engage in resilience may inform interventions promoting optimal well-being.

Associations Between Health Insurance Coverage with HIV Detection and Prevention Behaviors Among Individuals with Undiagnosed HIV or at Increased Risk for HIV Infection in the USA

BACKGROUND

Improving HIV detection and prevention remains a critical public health initiative that requires policy-based solutions. This study sought to compare HIV detection/prevention behaviors before and after healthcare reform in Massachusetts, USA, among heterosexually active persons - the group with the highest reported number of undiagnosed HIV cases. The current study sought to (1) characterize differences in insurance coverage and HIV detection/prevention behaviors between cycles 1 (2006) to 5 (2019); (2) evaluate socio-demographic disparities in insurance coverage accounting for cycle; and (3) evaluate associations between health insurance coverage and HIV detection/prevention behaviors accounting for cycle and socio-demographics.

METHODS

This is a secondary analysis of the National HIV Behavioral Surveillance (NHBS) project: Boston HET cycle (i.e., made up of heterosexually active persons living in the Boston area) data. Descriptive, bivariate (e.g., chi-square), and multiple logistic and negative binomial loglink regression analyses were conducted.

RESULTS

In chi-square analyses with post hoc Bonferroni tests, the proportion of participants with current health insurance significantly increased from cycle 1 (77%) to cycle 2 (95%), p < .001. In the regression models that controlled for NHBS cycle, 1-year change in age (adjusted odds ratio [aOR] = 1.03, 95% confidence interval [CI] = 1.02, 1.05), female gender (aOR = 3.41, 95% CI = 2.48, 4.69), and change in education category (aOR = 1.19, 95% CI = 1.02, 1.39) were associated with a higher likelihood of having health insurance. In regression models that controlled for cycle, age, gender, and education, participants with health insurance were more likely than those without insurance to report seeing a medical provider in the past year (aOR = 3.49, 95% CI = 2.32, 4.66), ever having an HIV test (aOR = 1.52, 95% CI = 0.35, 2.69) and more frequent HIV testing in the past 2 years (incidence rate ratio [IRR] = 1.44, 95% = 1.14, 1.82). Participants with health insurance did not differ from those without insurance in number of vaginal condomless sex partners (IRR = 1.16, 95% CI = 0.95, 1.41) but did report more condomless anal sex partners in the past year (IRR = 1.97, 95% CI = 1.46, 2.65).

CONCLUSIONS

This study demonstrates how health insurance coverage is positively associated with HIV detection and prevention relevant to both US and international efforts to end the HIV epidemic.

Internet Recruitment of a Diverse Population of Lesbian, Gay, and Bisexual Nurses in a Study of Substance Use and Minority Stress

INTRODUCTION

There is a lack of lesbian, bisexual and gay (LGB)-focused nursing research, in part, because the population is traditionally difficult to access. This article explores the effectiveness, benefits, and limitations of online recruitment of a distinct population of LGB-identified nurses in a study of substance use and minority stress.

METHODOLOGY

A sample of nurses who self-identified as LGB were recruited for an online survey using organic Facebook outreach. A $5 Amazon gift card was offered as an incentive. Facebook insights data and demographic data were analyzed.

RESULTS

Within 96 hours, 394 participants had completed the 101-question online survey. The majority (n = 269, 68.6%) reported accessing the survey through Facebook. Email (n = 79, 20.2%) and word of mouth (n = 44, 11.2%) also contributed to recruitment.

DISCUSSION

The effectiveness of this Facebook recruitment protocol speaks to the importance of social media, survey incentives, and the "power of visibility" in recruitment of this population.

Acute kidney injury following endovascular intervention for peripheral artery disease

BACKGROUND

The incidence of, and risk factors for, acute kidney injury (AKI) after endovascular intervention for peripheral artery disease (PAD) remain unknown. The aim of this study was to assess the proportion of patients who develop AKI and explore the risk factors.

METHODS

Prospectively collected data on patients undergoing femoropopliteal endovascular intervention for symptomatic PAD across three vascular centres were analysed. The proportion of patients developing AKI (according to the Kidney Disease Improving Global Outcomes definition) within 48 h, and the proportion developing the composite Major Adverse Kidney Events (MAKE) endpoints (death, dialysis, drop in estimated glomerular filtration rate at least 25 per cent) at 30 days (MAKE30) and remains 90 days (MAKE90) were calculated. Multivariable regression analysis was used to assess predictors of AKI, and the association between AKI and death.

RESULTS

Some 2041 patients were included in the analysis. AKI developed in 239 patients (11.7 per cent), with 47 (2.3 per cent) requiring dialysis within 30 days, and 18 (0.9 per cent) requiring ongoing dialysis. The MAKE30 and MAKE90 composite endpoints were reached in 358 (17.5 per cent) and 449 (22.0 per cent) patients respectively. Risk factors for AKI were age, sex, congestive heart failure, chronic limb-threatening ischaemia, emergency procedure, and pre-existing chronic kidney disease. AKI, dementia, congestive heart failure, and major amputation were risk factors for medium-term mortality.

CONCLUSION

AKI is a common complication after intervention for PAD and is associated with medium-term mortality.

Structural Issues Associated with Pre-exposure Prophylaxis Use in Men Who Have Sex with Men

BACKGROUND

Limited access to healthcare has been associated with limited uptake of pre-exposure prophylaxis (PrEP) for HIV among men who have sex with men (MSM). This descriptive analysis examined, in a near universal healthcare setting, differences between MSM reporting using versus not using PrEP in the past 12 months.

METHOD

Data come from the 2017 Boston sample of the National HIV Behavioral Surveillance (NHBS) system, containing a venue-based and time-spaced sample of 530 MSM. The analysis used descriptive frequencies and tests of bivariate associations by PrEP use using Fisher's exact test.

RESULTS

Five hundred four respondents had data necessary to determine if PrEP was indicated, and 233 (43.9%) had an indication for PrEP. Of these 233 participants, 117 (50.2%) reported using PrEP in the past 12 months. Not being out, in terms of disclosing one's sexual orientation to a healthcare provider, lack of health insurance, limited access to healthcare, and history of incarceration were all significantly associated with not using PrEP in the past 12 months. Race/ethnicity was not significantly associated with PrEP use in the past 12 months.

CONCLUSIONS

In the setting of Massachusetts healthcare expansion and reform, and in a sample somewhat uncharacteristic of the population of individuals experiencing difficulties accessing PrEP, structural and demographic factors remain potent barriers to PrEP uptake. Targeted PrEP expansion efforts in Massachusetts may focus on identifying vulnerable subgroups of MSM (e.g., underinsured or criminal justice system-involved MSM) and delivering evidence-based interventions to reduce stigma and promote disclosure of same-sex behavior in healthcare settings.

A Review of Factors Associated with Age of First Injection

Injection drug use (IDU) is of increasing public health concern in the United States. Misuse of and addiction to opioids has contributed to declining life expectancies and rebounding risk of HIV and HCV acquisition among people who inject drugs. While some effective treatment strategies for individuals with substance use disorders have been established, effective interventions to prevent IDU require greater tailoring to subpopulations and social contexts. To better understand contextual variables associated with initiation of IDU, we conducted a narrative review of the existing literature that assessed correlates of age of first injection. We found sixteen studies that met our inclusion criteria. Across studies, later IDU initiation was associated with being African American and female, while early initiation was associated with earlier illicit substance use, childhood trauma, and incarceration. We also found that early initiation was associated with riskier substance-using behaviors, though the findings were mixed with respect to differences between early and late initiates in infectious disease prevalence. These correlates of age of first injection can potentially inform tailored injection prevention strategies. By identifying the features and behaviors of relevant subpopulations before they inject, interventions to prevent IDU could become more effective.

Substance Use and Minority Stress in a Population of Lesbian, Gay and Bisexual Nurses

The aim of this study was to explore the incidence of problematic substance use (PSU) and the relationship between level of substance use, minority stress, and general stressors in a population of lesbian, gay and bisexual (LGB) identified nurses. Methods: A national, convenience sample of 394 self-identified LGB nurses completed an online survey in March 2019. Using data from the ASSIST V3.1 measurement tool, the incidence of problematic and non-problematic tobacco, alcohol and illicit substance use was described as a percentage of respondents in each group. Hierarchical regression assessed the impact of demographic variables, sexual orientation, gender identity, race/ethnicity, and level of substance use. Multiple regression assessed the impact of general stressors, minority stress processes, including coping and social support and internalized homophobia, on level of substance use. Results: The incidence of PSU was higher in this population of LGB-identified nurses than previously described in either the general population of nurses or the general LGB population. Demographic variables and minority status had variable associations with level of tobacco, alcohol and illicit substance use. Components of Meyer's minority stress model had a stronger and more consistent association with level of tobacco, alcohol and illicit substance use than general stress. Predictors of level of substance use across groups suggest community involvement may be significant. These results have potential implications for public health and the prevention and treatment of substance use in LGB-identified nurses.

Pilot Randomized Controlled Trial of a Syndemics Intervention with HIV-Positive, Cocaine-Using Women

This pilot randomized controlled trial examined the feasibility and acceptability of a Syndemics intervention targeting the intersection of stimulant use, trauma, and difficulties with HIV disease management in cocaine-using women. All participants received contingency management (CM) for 3 months with financial incentives for stimulant abstinence during thrice-weekly urine screening and refilling antiretroviral medications monthly. Sixteen participants were randomized to complete four expressive writing (n = 9) or four neutral writing (n = 7) sessions delivered during the CM intervention period. Completion rates for writing sessions were high (15 of 16 women completed all four sessions) and engagement in CM urine screening was moderate with women randomized to expressive writing providing a median of 11 non-reactive urine samples for stimulants. There were non-significant trends for those randomized to expressive writing to provide more CM urine samples that were non-reactive for stimulants, report greater decreases in severity of cocaine use, and display reductions in log₁₀ HIV viral load at 6 months. Although the Syndemics intervention was feasible and acceptable to many women, qualitative interviews with eligible participants who were not randomized identified structural and psychological barriers to engagement. Further clinical research is needed to test the efficacy of Syndemics interventions with HIV-positive, cocaine-using women.

A Mixed Methods Study of Anticipated and Experienced Stigma in Health Care Settings Among Women Living with HIV in the United States

Among places where people living with HIV experience and anticipate HIV-related stigma, stigma in health care settings may be particularly harmful. Utilizing an exploratory sequential mixed methods approach, we conducted interviews (n = 76) and questionnaires (N = 460) with older adult women living with HIV enrolled in the Women's Interagency HIV Study in Birmingham, AL; Jackson, MS; Atlanta, GA; and San Francisco, CA. Interviews addressed facilitators and barriers to HIV treatment adherence, including HIV-related stigma. Qualitative data were coded using thematic analysis. Questionnaires assessed self-reported antiretroviral therapy (ART) adherence and experienced and anticipated HIV-related stigma from various sources (i.e., health care personnel, family, partner, and community). Covariate-adjusted logistic regression analyses examined total and mediated effects of stigma on ART adherence. Interviewees described fears and experiences of stigma in health care settings; including privacy violations, disrespect for patient autonomy, and reproductive coercion; and how these influenced their adherence to HIV treatment recommendations. Experienced and anticipated HIV-related stigma in health care settings were associated with suboptimal (or <95%) ART adherence in separate models controlling for experienced or anticipated stigma, respectively, from other sources. When entered together, only anticipated stigma in health care settings was associated with suboptimal ART adherence, controlling for anticipated and experienced stigma from other sources. The effect of anticipated stigma in health care settings on suboptimal ART adherence may work through the pathways of lower adherence self-efficacy, higher depressive symptoms, and higher coping by substance use. These findings indicate that interventions should promote cultures of acceptance within health care settings and resilience-based strategies for women to combat stigma and promote life-sustaining behaviors.

Randomized controlled trial of a positive affect intervention for people newly diagnosed with HIV

OBJECTIVE

We conducted a randomized controlled trial to determine whether IRISS (Intervention for those Recently Informed of their Seropositive Status), a positive affect skills intervention, improved positive emotion, psychological health, physical health, and health behaviors in people newly diagnosed with HIV.

METHOD

One-hundred and fifty-nine participants who had received an HIV diagnosis in the past 3 months were randomized to a 5-session, in-person, individually delivered positive affect skills intervention or an attention-matched control condition.

RESULTS

For the primary outcome of past-day positive affect, the group difference in change from baseline over time did not reach statistical significance (p = .12, d = .30). Planned secondary analyses within assessment point showed that the intervention led to higher levels of past-day positive affect at 5, 10, and 15 months postdiagnosis compared with an attention control. For antidepressant use, the between group difference in change from baseline was statistically significant (p = .006, d = -.78 baseline to 15 months) and the difference in change over time for intrusive and avoidant thoughts related to HIV was also statistically significant (p = .048, d = .29). Contrary to findings for most health behavior interventions in which effects wane over the follow up period, effect sizes in IRISS seemed to increase over time for most outcomes.

CONCLUSIONS

This comparatively brief positive affect skills intervention achieved modest improvements in psychological health, and may have the potential to support adjustment to a new HIV diagnosis. (PsycINFO Database Record

Neurocognitive, psychiatric, and substance use characteristics in opioid dependent adults

AIMS

To describe neurocognitive function among opioid-dependent adults seeking buprenorphine treatment and to explore the impact of lifetime psychiatric conditions on neurocognitive function. To explore the additive interaction of patient-based characteristics that may help to inform treatment.

DESIGN

Cross-sectional assessment of neurocognitive function, substance use, and psychiatric characteristics of adults seeking buprenorphine treatment within substance use treatment centers in New York City.

PARTICIPANTS

Thirty-eight opioid-dependent adults seeking buprenorphine treatment.

MEASUREMENTS

A comprehensive battery, which included measures of executive functioning, learning, memory, verbal fluency, attention, processing speed, and motor functioning were administered. The Wide Range Achievement Test-Third Edition, the Composite International Diagnostic Interview, and an audio computer assisted structured interview were also completed. Correlations and independent sample t-tests were used to ascertain group differences.

FINDINGS

Thirty-nine percent of participants were impaired in global neurocognitive function (n=15). Over one third were impaired in either: learning (n=28), memory (n=26), executive functioning (n=17), motor functioning (n=17), attention/working memory (n=14) or verbal fluency (n=12). Lifetime history of alcohol dependence was associated with impairment in global neurocognitive, executive functioning, and motor functioning. Lifetime history of cocaine dependence was associated with impairment in executive functioning and motor functioning (all p's<0.05). Major depressive disorder history was not associated with neurocognitive impairment.

CONCLUSIONS

Among this sample of opioid-dependent adults, there were high rates of global and domain-specific neurocognitive impairment, with severe impairment in learning and memory. Lifetime alcohol and cocaine dependence were associated with greater neurocognitive impairment, particularly in executive functioning. Because executive functioning is critical for decision-making and learning/memory dysfunction may interfere with information encoding, these findings suggest that opioid-dependent adults may require enhanced support for medical decision-making.

Reducing barriers to hepatitis C treatment among drug users: an integrated hepatitis C peer education and support program

This report describes an innovative HCV Peer Educator Program that facilitates education, support, and engagement in HCV treatment among patients in an opioid treatment program. Integrating peer educators in a collaborative manner with close supervision holds promise as a model to reduce barriers to HCV treatment among drug users.

The common sense model applied to hepatitis C: a qualitative analysis of the impact of disease comparison and witnessed death on hepatitis C illness perception

BACKGROUND

Hepatitis C virus (HCV) accounts for 15,000 deaths in the United States yearly because people living with HCV are not identified in time to seek treatment, are ineligible for or refuse treatment, or face structural impediments to obtaining treatment such as lack of access to health care or lack of insurance. People who inject drugs (PWID) comprise a large proportion-estimates of up to 60-70%-of current and new HCV infected individuals and face many barriers to completing HCV treatment.

METHODS

We conducted 30 qualitative semi-structured interviews of current and former PWID seeking HCV treatment at an opioid-agonist treatment facility in New York City. We used thematic analysis, informed by grounded theory, to examine perceptions of HCV and decisions to initiate HCV treatment. We analyzed the themes that emerged via the common sense model (CSM) of illness perception theoretical framework.

RESULTS

Using thematic analyses, two major themes emerged related to engagement in HCV treatment. First, participants independently compared HCV to HIV, and in so doing, emphasized the potential fatality of HCV and the need for treatment. Second, participants described witnessing others suffer or die from untreated HCV and expressed how these recollections impacted their desire to undergo treatment themselves. Together, these themes contributed to the way participants perceived HCV and informed their decisions to initiate treatment. Both themes reflect the CSM's "self-regulation" process, which posits that understanding the causes and consequences of an illness impacts one's ability to seek treatment to overcome this illness state.

CONCLUSIONS

This paper offers insight into how clinicians can better understand and utilize HCV illness perceptions to evaluate willingness to engage in HCV treatment among PWID considering antiviral treatment modalities.

It made my life a little easier: primary care providers' beliefs and attitudes about using opioid treatment agreements

OBJECTIVE

To understand primary care providers (PCPs)' experiences, beliefs, and attitudes about using opioid treatment agreements (OTAs) for patients with chronic pain.

DESIGN

Qualitative research study.

PARTICIPANTS

Twenty-eight internists and family medicine physicians at two health centers.

APPROACH

Semistructured telephone interviews, informed by the Integrative Model of Behavioral Prediction. Themes were analyzed using a Grounded Theory approach, and similarities and differences in themes were examined among OTA adopters, nonadopters, and selective adopters.

RESULTS

Participants were 64 percent female and 68 percent white, and practiced for a mean of 9.5 years. Adoption of OTAs varied: seven were adopters, five were nonadopters, and 16 were selective adopters. OTA adoption reflected PCPs' beliefs and attitudes in the following three thematic categories: 1) perceived effect of OTA use on the therapeutic alliance, 2) beliefs about the utility of OTAs for patients or providers, and 3) perception of patients' risk for opioid misuse. PCPs commonly believed that OTAs were useful for physician self-protection, but few believed that they prevent opioid misuse. Selective adopters expressed ambivalent beliefs and made decisions about OTA use for individual patients based on both observed data and a subjective sense of each patient's risk for misuse.

CONCLUSIONS

Substantial variability in PCP use of OTAs reflects differences in PCP beliefs and attitudes. Research to understand the impact of OTA use on providers, patients, and the therapeutic alliance is urgently needed to guide best practices.

Clinician-assessed depression and HAART adherence in HIV-infected individuals in methadone maintenance treatment

BACKGROUND

The impact of measurement methods on the relationship between depression and HIV treatment adherence has not been adequately examined.

PURPOSE

The purpose of this paper is to examine the relationship between clinician- and patient-rated depression and HIV medication adherence.

METHODS

The participants were 91 HIV-infected individuals in methadone maintenance. Depression was assessed via clinician ratings (Clinical Global Impression Scale and Montgomery Asberg Depression Rating Scale) and self-report (Beck Depression Inventory-Short Form). Clinicians rated substance abuse using the Clinical Global Impression Scale and a structured interview. HIV medication adherence was measured over the following 2 weeks using electronic caps.

RESULTS

Each unit increase in the Clinical Global Impression Scale was associated with 75% increased odds of nonadherence (OR=1.75, p=0.002, 95% CI=1.23-2.48). Similarly, for each standard deviation Montgomery Asberg Depression Rating Scale increase, there was a 2.6-fold increased odds of nonadherence (OR=2.60, p=0.001, 95% CI=1.45-4.67). Substance abuse and self-reported depression severity were not significantly related to adherence.

CONCLUSIONS

Clinician-rated depression severity was a strong predictor of nonadherence. Assessment methods may influence the relationship between depression and HIV nonadherence.

Association of autistic spectrum disorders with dystrophinopathies

Parents of 85 boys with dystrophinopathies and 51 sibling controls completed the Social Communication Questionnaire, describing child behaviors associated with autism spectrum disorders and a rating of parental stress. Twenty-one boys with dystrophinopathies and no siblings received scores above the cut-point for possible autistic spectrum disorders. Mothers of identified children were given detailed interviews using the Autism Diagnostic Interview-Revised, and 16 boys (about 19% of the sample) met the criteria for autism spectrum disorders. Significant qualitative abnormalities in reciprocal social interactions and communication were evident in all, whereas restricted and repetitive behaviors were generally less pronounced in the group. Moreover, parents of boys with dystrophinopathy and autism spectrum disorders demonstrated significantly higher ratings of stress than parents of boys with dystrophinopathy alone. Increased attention to behavioral concerns associated with dystrophinopathies is necessary to ensure the well-being of the whole family.

Personalized dosing of cyclophosphamide in the total body irradiation-cyclophosphamide conditioning regimen: a phase II trial in patients with hematologic malignancy

This study investigates the efficacy and safety of personalized cyclophosphamide (CY) dosing in 50 patients receiving CY along with total body irradiation (TBI). Participants received CY 45 mg/kg with subsequent therapeutic drug monitoring using Bayesian parameter estimation to personalize the second CY dose to a target area under the curve (AUC) for carboxyethylphosphoramide mustard (CEPM) (a reporter molecule for CY-derived toxins) and for hydroxycyclophosphamide (to ensure engraftment). The mean second CY dose was 66 mg/kg; the total dose ranged from 45 to 145 mg/kg. After completion of this phase II study, we compared participants' clinical outcomes with those of concurrent controls (n = 100) who received TBI along with standard CY doses of 120 mg/kg. Patients receiving personalized CY dosing had significantly lower postconditioning peak total serum bilirubin (P = 0.03); a 38% reduction in the hazard of acute kidney injury (AKI) (P = 0.03); and nonrelapse and overall survival rates similar to those in the controls (P = 0.70 and 0.63, respectively) despite the lower doses of CY administered to most of the patients in the personalized dosage group.

Pharmacogenomic associations in ABCB1 and CYP3A5 with acute kidney injury and chronic kidney disease after myeloablative hematopoietic cell transplantation

Renal disease is a major complication in patients following myeloablative allogeneic hematopoietic cell transplantation (HCT). Post-HCT patients receive immunosuppressive regimens containing calcineurin inhibitor (CNIs), cyclosporine or tacrolimus, for graft-versus-host disease prophylaxis. In this retrospective trial, we investigated pharmacogenomic associations in the multidrug resistance (ABCB1) and cytochrome P450 3A5 (CYP3A5) genes and acute kidney injury (AKI) and chronic kidney disease (CKD) in a cohort of 121 patients. ABCB1 and CYP3A5 are responsible for the renal disposition of CNIs, which are known to be nephrotoxic. AKI was defined as doubling of baseline serum creatinine during the first 100 days post-HCT, and CKD as at least one glomerular filtration rate <60 ml/min/m2 between 6 and 18 months post-HCT. Patients were genotyped for CYP3A5*1>*3 and ABCB1 single nucleotide polymorphisms (SNPs) (1199G>A, 1236C>T, 2677G>T/A and 3435C>T). Odds ratios were calculated using logistic regression. Haplotype estimation and univariate association analyses were performed because of strong ABCB1 linkage disequilibrium (LD). AKI occurred in 48 of 121 patients (39.7%) and CKD in 16 of 66 patients (24.2%). No pharmacogenomic associations were found between ABCB1 and CYP3A5 SNPs and the incidences of AKI or CKD. The degree of LD(r2) between ABCB1 SNPs was estimated as follows: 2677G>T/3435C>T (0.44), 1236C>T/3435C>T (0.42) and 1236C>T/2677G>T (0.72). ABCB1 1199G>A showed no LD to other SNPs (<0.05). No associations were found between the most common ABCB1 haplotypes and AKI or CKD. Since no significant pharmacogenomic associations were observed, tailoring CNIs dosing based on these genotypes is unlikely to lower significantly the risk of renal injury following myeloablative HCT.

Hypercalcemia during the osteogenic phase after rat marrow ablation coincides with increased bone resorption assessed by the NTx marker

Marrow ablation is a model of bone turnover in which the excavated tibial intramedullary cavity is rapidly and reproducibly filled by osteoblasts with new woven bone (days 6-8), which is then rapidly resorbed by osteoclasts (days 10-15). We showed previously (Magnuson et al., 1997) that marrow ablation induces a dramatic hypercalcemia and hypercalciuria in rats that unexpectedly peaked at the time of maximal osteogenesis and continued throughout the subsequent resorption phase. Based upon the amount of calcium mobilized and a peak of urinary hydroxyproline, we suggested that the hypercalcemia and hypercalciuria were due to increased systemic osteoclastic bone resorption induced by marrow ablation. We now apply a new enzyme-linked immunosorbent assay for rodent alpha(2)(I) N-telopeptide (NTx), a marker of bone resorption, to the marrow ablation model to demonstrate that excretion of NTx parallels that of calcium release in the operated control group. Specifically, maximal NTx/creatinine excretion coincides with the onset of hypercalcemia on days 7-8. A peak of NTx was also observed in methylprednisolone- and deflazacort-treated ablated animals. Analyses for urinary free deoxypyridinoline crosslink failed to detect a significant ablation-induced change in excretion. Interleukin 6 activity was increased in all operated control and glucocorticoid-treated groups after marrow ablation, whereas serum parathyroid hormone remained at presurgical levels in operated controls throughout the 15-day study period. The NTx results confirm that bilateral tibial marrow ablation induces a burst of extratibial bone resorption and hypercalcemia 7-8 days later. We have estimated that the osteogenic phase of the ablation model deposits 40 mg of calcium as hydroxyapatite crystals within the intramedullary cavity on days 6-8; this represents 33%-50% of the total blood calcium content of a young rat. We hypothesize that the size and rapidity of this demand for ionized calcium is met through an extratibial bone resorption pathway of osteoclast formation and activation that anticipates and fulfills this need, and that is initiated at the time of marrow ablation.