Attrition in geriatric research: how important is it and how should it be dealt with?

Attrition, defined as a total loss to follow-up of participants, is a potential major bias in clinical trials. Participants can be lost for many reasons (death, illness, worsened health, refusal, withdrawal, lost to follow up). Attrition may be higher in older populations, so geriatric researchers should pay particular attention to the difficulties it raises. For a proper interpretation of research findings, a detailed analysis of the type of attrition observed and its possible determinants is essential, to determine if attrition has occurred at random or if it is associated to certain patient or treatment characteristics. This paper aims to review different causes of attrition, its prevalence among studies in different elderly populations, and its consequences on research findings. In addition, strategies used to minimise attrition (tracking, bonding, incentives) are discussed, and methods proposed to take this phenomenon into account are proposed.

The relationship of serum cobalamin to methylmalonic acid concentrations and clinical variables in cats.

BACKGROUND: Serum cobalamin concentration [CBL] suggests CBL deficiency in cats but serum methylmalonic acid concentration [MMA] more accurately indicates CBL deficiency. OBJECTIVE: To examine the ability of [CBL] to predict CBL deficiency defined by increased [MMA], and relationships of [CBL] and [MMA] with select clinical and clinicopathological variables. ANIMALS: One hundred sixty-three client-owned cats with [CBL] measurements, 114 cats with simultaneous [MMA] measurements; 88 cats with medical information. METHODS: Prospectively collected [CBL] and [MMA] were compared using scatter plots, receiver operating characteristic and correlative analyses with historical [CBL] thresholds and those identified in the study. [CBL] and [MMA] were compared retrospectively to specific clinical and clinicopathological variables. RESULTS: [CBL] correlated negatively with [MMA] (τ = -0.334, P < .0001). [MMA] ≥ 1,343 nmol/L identified CBL deficiency. [CBL] = 209 pg/mL optimized sensitivity (0.51), specificity (0.96), PPV (0.89), and NPV (0.74) for detecting [MMA] ≥ 1,343 nmol/L. Prevalence of CBL deficiency was 42% (48/114) when defined by [MMA] ≥ 1,343 nmol/L versus 23% (27/114) by [CBL] ≤ 209 pg/mL. Unexpectedly, 23 and 45% of 48 cats with [MMA] ≥ 1,343 nmol/L had [CBL] > 900 pg/mL and 290 pg/mL (historical thresholds). [CBL] correlated with mean corpuscular volume (τ = -0.199, P = .013) and [MMA] with hematocrit (τ = -0.28, P = .006). CONCLUSIONS AND CLINICAL IMPORTANCE: Cobalamin deficiency ([MMA] ≥ 1,343 nmol/L) occurred in 42% of cats and is predicted with high specificity by [CBL] ≤ 209 pg/mL. CBL status correlates with microcytosis and anemia. Discordance between [CBL] and [MMA] cautions against relying on any single marker for determining CBL status.

Suspected contact scrotal dermatitis in the dog: a retrospective study of 13 cases (1987 to 2003).

OBJECTIVES: The aim of this study was to assess the clinical and aetiological aspects of contact dermatitis of the scrotum in dogs. METHODS: The medical records of 13 dogs with suspected scrotal contact dermatitis were retrospectively included in the study. For each case, historical findings, results of physical and dermatological examination and of avoidance tests as well as follow-up were included. Results of re-exposure tests and patch tests were also included when available. RESULTS: Avoidance tests to various suspected substances such as floor detergents, bleach, cement, laundry detergent and plastic fabric were performed and led to clinical improvement in all patients. Provocative re-exposure was performed in six cases, with five positive responses. Patch tests were undertaken in three of the five re-exposed cases, with two responding positively. CLINICAL SIGNIFICANCE: Scrotal skin is thin and with few hair follicles, and is therefore very susceptible to contact dermatitis. A range of substances can induce contact dermatitis. The diagnosis of contact dermatitis is made by results of avoidance and/or provocation tests and/or patch tests. Once an aetiological agent has been identified, treatment is straightforward consisting of avoidance of this agent.