Inherited haemoglobin variants in a South African population

Causes of Moderate and Severe Anaemia in a High-HIV and TB-Prevalent Adult Population in the Eastern Cape Province, South Africa

BACKGROUND

Anaemia affects one in four adults in South Africa, with a higher prevalence in persons with HIV and tuberculosis. The aim of this study is to characterise the causes of anaemia in primary care and a district hospital setting.

METHODS

A cross-sectional study design investigated a purposive sample of adult males and non-pregnant females at two community health centres and a hospital casualty and outpatients. Fingerpick blood haemoglobin was measured with HemoCueHb201+. Those with moderate and severe anaemia underwent clinical examination and laboratory tests.

RESULTS

Of 1327 patients screened, median age was 48 years, and 63.5% were female. Of 471 (35.5%) with moderate and severe anaemia on HemoCue, 55.2% had HIV, 16.6% tuberculosis, 5.9% chronic kidney disease, 2.6% cancer, and 1.3% heart failure. Laboratory testing confirmed 227 (48.2%) with moderate and 111 (23.6%) with severe anaemia, of whom 72.3% had anaemia of inflammation, 26.5% iron-deficiency anaemia, 6.1% folate deficiency, and 2.5% vitamin B12 deficiency. Overall, 57.5% had two or more causes of anaemia. Multivariate modelling showed that patients with severe anaemia were three times more likely to have tuberculosis (OR = 3.1, 95% CI = 1.5-6.5; p-value = 0.002). Microcytosis was present in 40.5% with iron deficiency, macrocytosis in 22.2% with folate deficiency, and 33.3% with vitamin B12 deficiency. The sensitivities of the reticulocyte haemoglobin content and % hypochromic red blood cells in diagnosing iron deficiency were 34.7% and 29.7%, respectively.

CONCLUSIONS

HIV, iron deficiency, and tuberculosis were the most prevalent causes of moderate and severe anaemia. The majority had multiple causes. Iron, folate, and vitamin B12 deficiencies should be identified by biochemical testing rather than by red cell volume.

Performance of glycated albumin for type 2 diabetes and prediabetes diagnosis in a South African population

OBJECTIVE

To assess the utility of glycated albumin (GA%) as a diagnostic marker of type 2 diabetes and prediabetes in an African population.

METHODS

GA% levels were determined in a sample of 1294 mixed ancestry adults (74.2% women) residing in Cape Town using an enzymatic method. The participants' glycemic status was based on oral glucose tolerance test (OGTT).

RESULTS

The mean age was 47.8 years with a mean body mass index (BMI) of 28.7 kg/m². Obesity was more pronounced in the screen-detected diabetes and prediabetes groups with mean BMI's of 32.5 kg/m² and 31.5 kg/m² respectively. The optimal thresholds of GA% to diagnose screen-detected diabetes and prediabetes, were 14.90% and 12.75% respectively. For screen-detected diabetes, the C-statistic was higher for HbA1c than GA% (p = .034) with values of 0.899 (95% CI 0.855-0.943) and 0.873 (0.782-0.892) respectively. The agreement between GA% and HbA1c at their optimal thresholds for diagnosing screen-detected diabetes, was kappa = 0.33 (95% CI 0.26-0.40) and was higher than the agreement for prediabetes, kappa = 0.16 (0.11-0.21). The performance of GA% to identify screen-detected diabetes at the optimal threshold of 14.90%, was 64.8% (95% CI 54.1%-74.6%) for sensitivity and 93.5% (92.0%-94.9%) for specificity. GA% was significantly less sensitive, but more specific than HbA1c (at the optimal threshold of 6.15%) for screen-detected diabetes diagnosis (both p ≤ .002 from McNemar tests for sensitivity and specificity comparisons).

CONCLUSIONS

GA% performed less well than HbA1c to identify participants with OGTT-diagnosed type 2 diabetes or prediabetes (HbA1c cut-off of 6.15% and 5.95% respectively) in this population.

Hemoglobin variants identified in the Uganda Sickle Surveillance Study

The Uganda Sickle Surveillance Study analyzed dried blood spots that were collected from almost 100 000 infants and young children from all 10 regions and 112 districts in the Republic of Uganda, with the primary objective of determining the prevalence of sickle cell trait and disease. An overall prevalence of 13.3% sickle cell trait and 0.7% sickle cell disease was recently reported. The isoelectric focusing electrophoresis technique coincidentally revealed numerous hemoglobin (Hb) variants (defined as an electrophoresis band that was not Hb A, Hb F, Hb S, or Hb C) with an overall country-wide prevalence of 0.5%, but with considerable geographic variability, being highest in the northwest regions and districts. To elucidate these Hb variants, the original isoelectric focusing (IEF) gels were reviewed to identify and locate the variant samples; corresponding dried blood spots were retrieved for further testing. Subsequent DNA-based investigation of 5 predominant isoelectric focusing patterns identified 2 α-globin variants (Hb Stanleyville II, Asn78Lys; Hb G-Pest, Asp74Asn), 1 β-globin variant (Hb O-Arab, Glu121Lys), and 2 fusion globin variants (Hb P-Nilotic, β31-δ50; Hb Kenya, ^Aγ81Leu-β86Ala). Compound heterozygotes containing an Hb variant plus Hb S were also identified, including both Hb S/O-Arab and HbS/Kenya. Regional differences in the types and prevalence of these hemoglobin variants likely reflect tribal ancestries and migration patterns. Algorithms are proposed to characterize these Hb variants, which will be helpful for emerging neonatal hemoglobinopathy screening programs that are under way in sub-Saharan Africa.

Implementation of POCT in the diabetic clinic in a large hospital

AIM

Point-of-care testing (POCT) is gaining renewed interest, especially in resource-limiting primary health care, due to rise in prevalence of communicable and non-communicable diseases hence POCT needscontinuous appraisal.

METHODS

Random glucose and glycated haemoglobin (HbA1c) were measured in 104 diabetic patients using standard laboratory multichannel analyzer 917. The utility of venous blood compared to capillary blood in measuring HbA1c was evaluated in a subset of 20 patients using a POCT device, DCA Vantage. Lastly, the POCT was validated against the laboratory multichannel analyser 917, in measurement of HbA1c in a second subset of 46 patients.

RESULTS

Random blood glucose levels and HbA1c levels moderately correlated (r2 = 0.56; p < 0.0001). Random glucose tests showed that 41% of the patients had poor glycaemic control while HbA1c showed 74%. Venous and capillary blood in HbA1c showed strong correlation (r2 = 0.89440; p < 0.001. There was also strong correlation (r = 0.9802; p < 0.0001) in HbA1c measured using the DCA Vantage and the standard laboratory analyser, Multichannel Analyser 917.

CONCLUSION

Venous or capillary blood can be used in POCT for HbA1c. POCT is ideal for monitoring glucose control and management of diabetes in resource-limited countries such as South Africa.

Developing and optimizing a decisional instrument using self-reported ancestry for carrier screening in a multi-ethnic society

PURPOSE

To develop a decisional instrument for ancestry-based cystic fibrosis and/or hemoglobinopathies carrier couple screening in The Netherlands.

METHODS

A flowchart (Instrument A) and a questionnaire with maps of geographical areas with originally high cystic fibrosis and hemoglobinopathies carrier frequencies (Instrument B), were developed to support participants in self-assessing their eligibility as a couple for carrier screening for cystic fibrosis and/or hemoglobinopathies. The outcome was compared to the self-reported origin of both partners' ancestors during an in-depth interview. Furthermore, preference for Instrument A or B was determined.

RESULTS

Of the 112 participants, 88% (99/112, 95% CI 82-94%) (Instrument A) and 91% (102/112, 95% CI 86-96%) (Instrument B), respectively, arrived at a decision in accordance with their ancestral origin, and 57% (64/112, 95% CI 48-66%) preferred Instrument B. A false negative proportion of 5.5% suggests that some carriers will exclude themselves from screening. Results might improve with minor changes in the instruments with regard to geographic specification, and availability of translated versions.

CONCLUSION

A decisional instrument to assess ancestry-based eligibility for cystic fibrosis and/or hemoglobinopathies carrier screening, is now available and can with slight adaptations be used in other countries. The instrument also takes into account the possibility of mixed ancestry.