The predictive value of low plasma copper and high plasma zinc in detecting zinc-induced copper deficiency

BACKGROUND

Zinc-induced copper deficiency is a condition whose diagnosis is often delayed allowing severe and usually irreversible neurology symptoms to develop. Plasma copper concentrations are usually low and plasma zinc concentrations high. The aim of this study was to measure the predictive value of this combination of results as a means of facilitating its early diagnosis.

METHODS

Low plasma copper (≤6 µmol/L) and high plasma zinc results (>18 µmol/L) were retrieved from the laboratory database from 2000 to 2014. Medical records and laboratory notes of the corresponding 20 patients found were accessed to determine which were likely to have zinc-induced copper deficiency.

RESULTS

Fifteen (75%) patients were diagnosed with zinc-induced copper deficiency which was symptomatic in 13. Of the five remaining patients, two were treated with zinc because of Wilson's disease which was the cause of hypocupraemia, two were treated parenterally with zinc, and insufficient information was available in the final patient.

CONCLUSIONS

The combination of a low plasma copper and high plasma zinc is strongly predictive for the diagnosis of zinc-induced copper deficiency. There is the therefore an opportunity for the reporting biochemist to facilitate in its earlier diagnosis so enabling treatment to be implemented before the condition deteriorates.

The promise and role of point of care testing to reduce the global burden of sickle cell disease through early diagnosis and linkage to care

Sickle cell disease (SCD) is a devastating and under-recognised global child health issue affecting over 300,000 infants annually, with the highest prevalence in India and sub-Saharan Africa. Most affected infants born in low- and middle-income countries (LMIC) lack access to SCD testing and die from complications in the first years of life without a formal diagnosis. The majority of deaths are preventable with early diagnosis and provision of inexpensive interventions. Despite global recognition of the urgent need, expansion of SCD newborn screening (NBS) programmes beyond the pilot stage has been obstructed by a dependence on an expensive and logistically challenging centralised laboratory testing model. Recently, several point-of-care tests (POCT) for SCD have been developed with promising field validation studies. Here, we summarise the state of POCT for SCD, review barriers and unanswered questions, and discuss optimal strategies for utilising POCT to address the growing global burden of SCD. There is an urgent need to prospectively evaluate the ability of POCT to reduce the morbidity and high early mortality of SCD. To impact a sustainable reduction to this end, it is essential to link a diagnosis with comprehensive SCD care, including wide and affordable access to affordable hydroxycarbamide therapy.

An evaluation of cardiopulmonary endurance and muscular strength in adults living with sickle cell disease

There have been limited investigations into exercise in sickle cell disease (SCD). In the general population, health is reflected in general physical fitness. It is unclear if the same associations are seen in people with SCD. Here, we report a cross-sectional assessment of two important measures of physical fitness, muscle strength and cardiorespiratory endurance, in adults with SCD. A total of 29 adults with SCD (aged 24-62 years; 72% female) completed cardiopulmonary and muscular strength testing using a cycle ergometer and an isokinetic dynamometer. Adults with SCD had lower median values for cardiorespiratory endurance (the median [interquartile range, IQR] peak oxygen uptake [VO₂ ] 16.1 [6.3] vs. 42.65 [11.3] ml/kg/min, p < 0.001) and knee strength (median [IQR] flexor torque 26.91[22.5] vs. 55.6 [22.7] Nm, p < 0.001) compared to controls and predicted values. Interestingly, there was a very positive association between muscular strength and peak VO₂ values for adults with SCD (r = 0.53, p = 0.003) suggesting these values may be useful in determining cardiopulmonary health.

Haemoglobin variants may cause significant differences in haemoglobin A1c as measured by high-performance liquid chromatography and enzymatic methods in diabetic patients: a cross-sectional study

Background We aimed to determine whether the discrepancy between haemoglobin A1c values determined by high-performance liquid chromatography and enzymatic haemoglobin A1c measurements in diabetic patients was clinically relevant. Methods We randomly recruited 1421 outpatients undergoing diabetic treatment and follow-up who underwent at least three haemoglobin A1c measurements between April 2014 and March 2015 at our clinic. In 6369 samples, haemoglobin A1c was simultaneously measured by HA-8160 and MetaboLead (enzymatic assay), and the values were compared. Results haemoglobin A1c measurements by high-performance liquid chromatography and enzymatic assay were strongly correlated (correlation coefficient: 0.9828, linear approximation curve y = 0.9986x - 0.2507). Mean haemoglobin A1c (6.8 ± 1.0%) measured by high-performance liquid chromatography was significantly higher than that measured by enzymatic assay (6.5 ± 1.0%, P < 0.0001). During the sample processing, four (0.3%) subjects presented consistently lower haemoglobin A1c values (<0.7%) by high-performance liquid chromatography than those from enzymatic assay. Of these, three had Hb Toranomon [β112 (G14) Cys→Trp]. The fourth had Hb Ube-2 [α68 (E17) Asn→Asp]. One other subject presented consistently higher haemoglobin A1c values (>1%) by high-performance liquid chromatography than those from enzymatic assay and was diagnosed with a -77 (T > C) mutation in the δ-globin gene. These unrelated asymptomatic subjects had normal erythrocyte profiles, without anaemia. Conclusions We showed that haemoglobin A1c values measured by high-performance liquid chromatography were significantly higher than those measured by enzymatic assay in diabetic subjects. However, when an oversized deviation (>0.7%) between glycaemic control status and haemoglobin A1c is apparent, clinicians should check the methods used to measure haemoglobin A1c and consider the possible presence of a haemoglobin variant.

Screening for haemoglobin disorders: One size may not fit all

Accurate laboratory screening for sickle cell disease and other haemoglobin disorders is expanding worldwide. Two new reports describe different methods and strategies for screening in Mali and Denmark, respectively, and their encouraging results suggest that countries should tailor their screening programmes according to local needs, resources and opportunities. Commentary on: Guindo et al. Potential for a large-scale newborn screening strategy for sickle cell disease in Mali: a comparative diagnostic performance study of two rapid diagnostic tests (SickleScan® and HemotypeSC®) on cord blood. Br J Haematol 2024;204:337-345 and Gravholt et al. The Danish national haemoglobinopathy screening programme: report from 16 years of screening in a low-prevalence, non-endemic region. Br J Haematol 2024;204:329-336.

The clinical spectrum of HbSC sickle cell disease-not a benign condition

Sickle cell disease (SCD) includes a group of heterogenous disorders that result in significant morbidities. HbSS is the most common type of SCD and HbSC is the second most common type of SCD. The prevalence of HbSC disease in the United States and United Kingdom is ~1 in 7174 births and 1 in 6174 births respectively. Despite its frequency, however, HbSC disease has been insufficiently studied and was historically categorized as a more 'mild' form of SCD. We conducted this study of HbSC disease as part of the NHLBI funded Sickle Cell Disease Implementation Consortium (SCDIC). The SCDIC registry included 2282 individuals with SCD, ages 15-45 years of whom 502 (22%) had HbSC disease. Compared with people with sickle cell anaemia (SCA), the study found that people with HbSC disease had a higher frequency of splenomegaly (n (%) = 169 (33.7) vs. 392 (22.1)) and retinopathy (n (%) = 116 (23.1) vs. 189 (10.6)). A Many people with HbSC also had avascular necrosis (n (%) = 112 (22.3)), pulmonary embolism (n (%) = 43 (8.6)) and acute chest syndrome (n (%) = 228 (45.4)) demonstrating significant disease severity. HbSC disease is more clinically severe than was previously recognized and deserves additional evaluation and targeted treatments.

EPAS1-mutated paragangliomas associated with haemoglobin disorders

We report a large series of 40 patients presenting EPAS1-mutated paraganglioma (PGL) in whom we investigated a cause underlying chronic hypoxia. Four patients suffered from hypoxaemic heart disease. In patients with available haemoglobin electrophoresis results, 59% presented with a haemoglobin disorder, including six with sickle cell disease, five with sickle cell trait and two with heterozygous haemoglobin C disease. Histological and transcriptomic characterization of EPAS1 tumours revealed increased angiogenesis and high similarities with pseudohypoxic PGLs caused by VHL gene mutations. Sickle haemoglobinopathy carriers could thus be at increased risk for developing EPAS1-PGLs, which should be taken into account in their management and surveillance.