The influence of hematological profiles on the transfusion management and mortality risk of mothers presenting to the obstetric unit of a South African tertiary medical facility.

BACKGROUND: Laboratory results are frequently abnormal in pregnant mothers. Abnormalities usually relate to pregnancy or associated complications. Hematological abnormalities and age in pregnancy may increase the likelihood for transfusion and mortality. STUDY DESIGN AND METHODS: Hematological profiles and transfusion history of pregnant mothers presenting to a tertiary hospital, were evaluated over 2 years. Age, anemia, leukocytosis and thrombocytopenia were assessed for transfusion likelihood. Iron deficiency and coagulation were assessed in transfused patients. Anemia, leukocytosis, thrombocytopenia, human immunodeficiency virus (HIV) and transfusion were assessed for mortality likelihood. RESULTS: There were 12,889 pregnant mothers included. Mothers <19-years-old had the highest prevalence of anemia (31.5%) and proportion of transfusions (19%). The transfusion likelihood was increased in mothers with anemia (odds ratios [OR] = 6.41; confidence intervals at 95% [95% CI] 5.46-7.71), leukocytosis (OR = 2.35; 95% CI 2.00-2.76) or thrombocytopenia (OR = 2.71; 95% CI 2.21-3.33). Mothers with prolonged prothrombin times received twice as many blood products as their normal counterparts (p = .03) and those with iron deficiency anemia five times more blood products (p < .001). Increased likelihood for mortality was seen in patients with anemia (OR = 4.15, 95% CI 2.03-8.49), leukocytosis (OR = 2.68; 95% CI 1.19-6.04) and those receiving blood transfusion (OR = 3.6, 95% CI 1.75-7.47). DISCUSSION: Adolescence, anemia, leukocytosis and thrombocytopenia expose mothers to a high risk for transfusion and/or mortality. These risk factors should promptly trigger management and referral of patients. Presenting hematological profiles are strong predictors of maternal outcome and transfusion risk.

Multicentre verification of haematology laboratory blood collection tubes during a global blood collection tube shortage.

INTRODUCTION: Verification of blood collection tubes is essential for clinical laboratories. The aim of this study was to assess performance of candidate tubes from four alternative suppliers for routine diagnostic haematology testing during an impending global shortage of blood collection tubes. METHODS: A multicentre verification study was performed in Cape Town, South Africa. Blood from 300 healthy volunteers was collected into K2 EDTA and sodium citrate tubes of BD Vacutainer® comparator tubes and one of four candidate tubes (Vacucare, Vacuette®, V-TUBE™ and Vacutest®). A technical verification was performed, which included tube physical properties and safety. Routine haematology testing was performed for clinical verification. RESULTS: Vacucare tubes did not have a fill-line indicator, Vacuette® tubes had external blood contamination on the caps post-venesection and Vacutest® tubes had hard rubber stoppers. K2 EDTA tubes of Vacuette®, Vacucare and Vacutest® performed similarly to the comparator. Unacceptable constant bias was seen for PT in Vacucare (95% CI -2.38 to -0.10), Vacutest® (95% CI -1.91 to -0.49) and Vacuette® (95% CI 0.10-1.84) tubes and for aPTT in Vacuette® (95% CI 0.22-2.00) and V-TUBE™ (95% CI -2.88 to -0.44). Unacceptable %bias was seen for aPTT in Vacucare (95% CI 2.78-4.59) and Vacutest® tubes (95% CI 2.53-3.82; desirable ±2.30), and in V-TUBE™ for mean cell volume (95% CI 1.15-1.47, desirable ±0.95%) and mean cell haemoglobin concentration (95% CI -1.65 to -0.93, desirable ±0.43%). CONCLUSION: Blood collection tubes introduce variability to routine haematology results. We recommend that laboratories use one brand of tube. Verification of new candidate tubes should be performed to ensure consistency and reliable reporting of results.

HIV false positive screening serology due to sample contamination reduced by a dedicated sample and platform in a high prevalence environment.

Automated testing of HIV serology on clinical chemistry analysers has become common. High sample throughput, high HIV prevalence and instrument design could all contribute to sample cross-contamination by microscopic droplet carry-over from seropositive samples to seronegative samples resulting in false positive low-reactive results. Following installation of an automated shared platform at our public health laboratory, we noted an increase in low reactive and false positive results. Subsequently, we investigated HIV serology screening test results for a period of 21 months. Of 485 initially low positive or equivocal samples 411 (85%) tested negative when retested using an independently collected sample. As creatinine is commonly requested with HIV screening, we used it as a proxy for concomitant clinical chemistry testing, indicating that a sample had likely been tested on a shared high-throughput instrument. The contamination risk was stratified between samples passing the clinical chemistry module first versus samples bypassing it. The odds ratio for a false positive HIV serology result was 4.1 (95% CI: 1.69-9.97) when creatinine level was determined first, versus not, on the same sample, suggesting contamination on the chemistry analyser. We subsequently issued a notice to obtain dedicated samples for HIV serology and added a suffix to the specimen identifier which restricted testing to a dedicated instrument. Low positive and false positive rates were determined before and after these interventions. Based on measured rates in low positive samples we estimate that before the intervention, of 44 117 HIV screening serology samples, 753 (1.71%) were false positive, declining to 48 of 7 072 samples (0.68%) post-intervention (p<0.01). Our findings showed that automated high throughput shared diagnostic platforms are at risk of generating false-positive HIV test results, due to sample contamination and that measures are required to address this. Restricting HIV serology samples to a dedicated platform resolved this problem.

High positive HIV serology results can still be false positive.

The consequences of falsely reactive HIV test results can be significant, for patients and healthcare providers. This case describes a diagnostic investigation of a patient with pronounced discordant HIV serological results, to determine HIV status. The fourth generation serological screening assay (Roche COBAS Elecsys HIV combiPT) had high positive results but confirmatory testing was negative (Abbott HIV Ag/Ab Combo). Five separate samples over 13 days were tested using multiple fourth generation HIV immunoassays and molecular tests for HIV-1 and HIV-2. Potential causes of falsely reactive serological results were investigated. Samples were sent to the manufacturer for analysis. The screening assay was positive on all samples with a very high signal to cut-off ratio (S/CO) of greater than 400. However, multiple serological and molecular assays did not detect HIV-1 or HIV-2 specific antibodies, antigen or nucleic acid. A recombinant immunochromatographic assay had faint reactivity to gp41 peptide and the manufacturer investigation reported cross-reactivity to one of the screening assay's synthetic peptides. Possible causes of the false positive result include cross reactivity to other antigens, including prior schistosomiasis infection, or the patient's previously excised ameloblastoma (a rare germ cell tumor of the jaw). This is a rare case of false high positive results on fourth-generation HIV serology testing due to high level non-specific reactivity to an isolated synthetic peptide component of the assay. It highlights the need for confirmatory testing even in settings with HIV high prevalence and awareness that false-positive serological results may have a high S/CO.