Stabilizing specimens for routine ammonia testing in the clinical laboratory

Hospital at Home programs: Decentralized inpatient care but centralized laboratory testing?

The Hospital at Home (HaH) program has experienced accelerated growth in major Canadian provinces, driven in part by technological advancements and evolving patient needs during the COVID-19 pandemic. As an increasing number of hospitals pilot or implement these innovative programs, substantial resources have been allocated to support clinical teams. However, it is crucial to note that the vital roles played by clinical laboratories remain insufficiently acknowledged. This mini review aims to shed light on the diverse functions of clinical laboratories, spanning the preanalytical, analytical, and post-analytical phases within the HaH program context. Additionally, the review will explore recent advancements in clinical testing and the potential benefits of integrating new technologies into the HaH framework. Emphasizing the integral role of clinical laboratories, the discussion will address the current barriers hindering their active involvement, accompanied by proposed solutions. The capacity and efficiency of the HaH program hinge on sustained collaborative efforts from various teams, with clinical laboratories as crucial team players. Recognizing and addressing the specific challenges faced by clinical laboratories is essential for optimizing the overall performance and impact of the HaH initiative.

Hyperammonemia in the Pediatric Emergency Department

ABSTRACT

Hyperammonemia is a serious clinical condition associated with significant morbidity and mortality. In the pediatric population, this is often caused by urea cycle disorders, acute liver failure, or other less common underlying etiologies. Children and teens with hyperammonemia can have a broad range of clinical findings, including vomiting, respiratory distress, and changes in mental status. As ammonia levels worsen, this presentation can progress to respiratory failure, encephalopathy, cerebral edema, seizures, and death. Given the risk of neurologic damage, timely identification and management of hyperammonemia is critical and includes initial resuscitation, early consultation with subspecialists, and initiation of appropriate therapies. It is important for pediatric emergency medicine providers to understand the clinical findings, causes, diagnosis, and management of hyperammonemia because they play a key role in the provision of effective, multidisciplinary care of these patients.

Air contamination of therapeutic drug monitoring assay reagents results in falsely high plasma ammonia levels

BACKGROUND

Accumulating evidence shows that contamination of blood samples by atmospheric ammonia affects blood ammonia test levels; however, reports on the effect of ammonia contamination of assay reagents are limited. Here, we aimed to clarify the effect of ammonia contamination of assay reagents, particularly the therapeutic drug monitoring (TDM) reagents, on the detection levels of blood ammonia using enzymatic assays.

METHODS

Ammonia gas was measured in the refrigerator compartment of the automatic analyser and the reaction tank water, probe wash water and drain outlets connected to the automatic analyser. At different time points following the closure of the cold storage, ammonia levels in quality control plasma samples were measured using three commercial assay reagents to evaluate the effect of air contamination. The distribution of evaporated ammonia in the reagent was measured using the CicaLiquid NH3 assay kit containing the assay reagent most affected by air contamination.

RESULTS

It was confirmed that ammonia gas was generated in the cold storage of the automatic analyser. More than half of the reagents detected >0.25 ppm ammonia, and the highest concentration was detected in the TDM reagent. The ammonia levels obtained using all three reagents increased significantly after 3 h of air contamination. The effect was resolved by measuring a 'dummy' sample or mixing the reagents by inversion.

CONCLUSIONS

We demonstrated that air contamination by TDM reagents placed in cold storage could result in significantly falsely high ammonia measurements. Preventing this effect would improve the accuracy of ammonia measurements.

Acute Presentation and Management of the Encephalopathic Child With an Undiagnosed Inborn Error of Metabolism

BACKGROUND

Inborn errors of metabolism (IEM) commonly present in infancy and, less commonly, later in life.

CASE REPORT

This case describes an IEM, specifically, ornithine transcarbamylase deficiency, in a previously healthy 7-year-old boy who presented to an emergency department with vomiting for approximately 24 h prior to admission. The child became progressively encephalopathic while in the emergency department, but an ammonia level was not obtained until several hours after admission. Irreversible brain damage with cerebral edema was already present at time of diagnosis, leading to death. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: This case emphasizes that acute hyperammonemia can rapidly cause irreversible neurological damage and, in the case of a newly encephalopathic pediatric patient, ammonia levels should be evaluated early to facilitate proper diagnostic tests and treatment.