Evaluation of Different Mixing Study Reagents and Dilution Effect in Lupus Anticoagulant Testing
Abstract
Until recently, the laboratory identification of lupus anticoagulants (LA) was not considered important. Often LA were regarded as a nuisance, resulting in factor assays and other coagulation tests with inconclusive results. However, the recognition of important clinical complications associated with the presence of LA has resulted in an emphasis on the detection of this phospholipid-dependent inhibitor. Most studies have evaluated the sensitivity of various screening or confirmatory procedures used in establishing the diagnosis of LA. The authors have focused on the variables involved in the mixing studies used to identify the presence of a circulating inhibitor. To detect the latter, attention to the ratio of patient plasma to normal plasma is important, particularly in the case of a minimally prolonged APTT. Also the source of "normal" plasma must be platelet poor to maximize sensitivity in the case of a weak LA.
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Brandt et al. also found less than satisfactory results when evaluating the three definitions of correction.
“Brandt et al, 3 in their evaluation of these 3 definitions of correction, also showed less than satisfactory results.”
From A “Percent Correction” Formula for Evaluation of Mixing Studies (2002) · cites this paper as [3]
In the aPTT 1:1 mixing study, the three suggested definitions of correction had poor sensitivity for detecting anticoagulant: 13%, 7%, and 7%.
“As shown in Table 7, all 3 suggested definitions of correction for evaluating the aPTT 1:1 mix 3 showed poor sensitivity (13%, 7%, and 7%, respectively) for detecting anticoagulant.”
From A “Percent Correction” Formula for Evaluation of Mixing Studies (2002) · cites this paper as [3]
Brandt et al. found that the 4:1 mix was ineffective for correcting the aPTT of the mixture and might misclassify factor deficiency as anticoagulant.
“while Brandt et al 3 found that the 4:1 mix was ineffective for correcting the aPTT of the mixture and that it might misclassify samples with factor deficiency as anticoagulant.”
From A “Percent Correction” Formula for Evaluation of Mixing Studies (2002) · cites this paper as [3]
Some anticoagulants have a time-dependent inhibitor effect in mixing studies.
“In addition, applicability of percent correction for evaluating the aPTT 4:1 mix testing after incubation also was studied to ascertain the described time-dependent inhibitor effect of some anticoagulants in mixing studies.3”
From A “Percent Correction” Formula for Evaluation of Mixing Studies (2002) · cites this paper as [3]
Factor deficiencies with markedly prolonged PT or aPTT may not be corrected to normal in a 1:1 mix.
“In contrast, factor deficiencies with a markedly prolonged PT or aPTT may not be corrected to normal in a 1:1 mix of PP with CNP. 3”
From A “Percent Correction” Formula for Evaluation of Mixing Studies (2002) · cites this paper as [3]
It was not clear from the publications which of the 1:1 or 4:1 mixing procedures was preferred.
“However, it was not clear from the publications which of the 2 procedures was preferred.”
From A “Percent Correction” Formula for Evaluation of Mixing Studies (2002) · cites this paper as [3]
A similar incubation effect in an aPTT mixing study of factor VIII inhibitor has been described.
“A similar incubation effect in an aPTT mixing study of factor VIII inhibitor has been described.3,10”
From A “Percent Correction” Formula for Evaluation of Mixing Studies (2002) · cites this paper as [3]
There is no uniform agreement on criteria for judging correction in mixing studies.
“There is no uniform agreement as to what criteria should be used to judge correction.3”
From A “Percent Correction” Formula for Evaluation of Mixing Studies (2002) · cites this paper as [3]
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“6,9 The presence of exogenous anticoagulants (heparin, direct thrombin inhibitors, Xa inhibitors), some antibiotics, C-reactive proteins, fibrin split products, or paraproteins in the test plasma can act as inhibitors in the mixing study; therefore, the results of mixing tests should be interpreted…”
- Authors
- Kaczor, D. A., Bickford, N. N., & Triplett, D. A.
- Affiliations
- Ball Memorial Hospital (US)
- Corresponding author
- Kaczor, Daniel A.
- Venue
- American Journal of Clinical Pathology
- Publisher
- Oxford University Press (OUP)
- Published
- 1991-03-01
- Volume
- 95
- Issue
- 3
- Pages
- 408-411
- ISSN
- 0002-9173 (ISSN-L)
- 1943-7722
- OpenAlex
- W104075595
- Cited by
- 46
- References
- 0
- Citations by year
- 2026: 1 · 2023: 2 · 2022: 3 · 2018: 1 · 2016: 1 · 2015: 1 · 2013: 1 · 2012: 1
- FWCI
- 3.41
- Type
- journal article
- Language
- en
- Open access
- closed
- Locations
- American Journal of Clinical Pathology (publishedVersion)
- PubMed (publishedVersion)
- Topics
- Health Sciences › Medicine › Rheumatology › Systemic Lupus Erythematosus Research
- Health Sciences › Medicine › Hematology › Blood Coagulation and Thrombosis Mechanisms
- Health Sciences › Medicine › Hematology › Hemophilia Treatment and Research
- Keywords
- lupus anticoagulant, mixing studies, dilution effect, activated partial thromboplastin time, platelet-poor plasma
- MeSH terms
- Blood Coagulation Factors, Humans, Indicators and Reagents, Partial Thromboplastin Time, Phospholipids, Platelet Count, Sensitivity and Specificity, Lupus Coagulation Inhibitor
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