Step-by-Step Diagnostic Sequence	25

Step-by-Step Diagnostic Sequence

On the basis of what has been said so far, the following guidelines for the diagnostic workup of hematological changes may be formulated:

1.The first step is quantitative determination of leukocytes (L), erythrocytes

(E) and thrombocytes (T). Because the normal range can vary so widely in individual cases (Table 2), the following rule of thumb should be observed:

A complete blood count (CBC) should be included in the baseline data, like blood pressure.

2.All quantitative changes in L + E + T call for a careful evaluation of the differential blood count (DBC). Since clinical findings determine whether a DBC is indicated, it may be said that:

A differential blood count is indicated:

By all unexplained clinical symptoms, especially

Enlarged lymph nodes or splenomegaly

Significant changes in any of

–Hemoglobin content or number of erythrocytes

–Leukocyte count

–Thrombocyte count

The only initial assumption here is that mononuclear cells with unsegmented nuclei can be distinguished from polynuclear cells. While this nomenclature may not conform to ideal standards, it is well established and, moreover, of such practical importance as a fundamental distinguishing criterion that it is worth retaining. A marked majority of mononuclear cells over the polynuclear segmented granulocytes is an unambiguous early finding.

The next step has to be taken with far more care and discernment: classifying the mononuclear cells according to their possible origin, lymphatic cells, monocytes, or various immature blastic elements, which otherwise only occur in bone marrow. The aim of the images in the Atlas section of this book is to facilitate this part of the differential diagnosis. To a great extent, the possible origins of mononuclear cells can be distinguished; however, the limits of morphology and the vulnerability to artifacts are also apparent, leaving the door wide open to further

26 Physiology and Pathophysiology of Blood Cells

diagnostic steps (specialist morphological studies, cytochemistry, immunocytochemistry. A predominance of mononuclear cell elements has the same critical significance in the differential diagnosis of both leukocytoses and leukopenias.

3.After the evaluation of the leukocytes, assessment of erythrocyte morphology is a necessary part of every blood smear evaluation. It is, naturally, particularly important in cases showing disturbances in the erythrocyte count or the hemoglobin.

4.After careful consideration of the results obtained so far and the patient's clinical record, the last step is the analysis of the cell composition of the bone marrow. Quite often, suspected diagnoses are confirmed through humoral tests such as electrophoresis, or through cytochemical tests such as alkaline phosphatase, myeloperoxidase, nonspecific esterase, esterase, or iron tests.

Bone marrow analysis is indicated when clinical findings and blood analysis leave doubts in the diagnostic assessment, for example in cases of:

Leukocytopenia

Thrombocytopenia

Undefined anemia

Tricytopenia, or

Monoclonal hypergammaglobulinemia

A bone marrow analysis may be indicated in order to evaluate the spreading of a lymphadenoma or tumor, unless the bloodstream already shows the presence of pathological cells.

5.Bone marrow histology is also rarely indicated (even more rarely than the bone marrow cytology). Examples of the decision-making process between bone marrow cytology and histology (biopsy) are shown in Table 3.

Often only histological analysis can show structural changes or focal infiltration of the bone marrow.

This is particularly true of the frequently fiber-rich chronic myeloproliferative diseases, such as polycythemia vera rubra, myelofibrosis– osteomyelosclerosis (MF-OMS), essential thrombocythemia (ET), and chronic myeloid leukemia (CML) as well as malignant lymphoma without hematological involvement (Hodgkin disease or blastic nonHodgkin lymphoma) and tumor infiltration.

	Step-by-Step Diagnostic Sequence	27
Table 3 Indications for a differential blood count (DBC), bone marrow aspiration, and biopsy
Indications	Procedures
All clinically unclear situations:	Differential blood count (DBC)

Enlarged lymph nodes or spleen

Changes in the simple CBC (penias or cytoses)

When a diagnosis cannot be made based on		Bone marrow analysis
	clinical findings and analysis of peripheral
	blood differential blood analysis, cytochem-
	istry, phenotyping, molecular genetics or
	FISH
		Bone marrow aspirate	Bone marrow
		(Morphology, phenotyp-	trephine biopsy
		ing, cytogenetics, FISH,	(Morphology, immuno-
		molecular genetics)	histology)
Punctio sicca ("dry tap")		not possible	+
	Aplastic bone marrow	not possible	+
Suspicion of myelodysplastic syndrome		+	(+) (e.g. hypoplasia)
	Pancytopenia	+	+
	Anemia, isolated	+	–
	Granulocytopenia, isolated	+	–
Thrombocytopenia, isolated (except ITP)		+	–
	Suspected ITP	(+) For therapy failure	–
	Suspected OMF/OMS	– (BCR-ABL in peripheral	+
		blood is sufficient)
	Suspected PV	– (BCR-ABL in peripheral	–
		blood is sufficient)
	Suspected ET	– (BCR-ABL in peripheral	+
		blood is sufficient)
	Suspected CML	– (BCR-ABL in peripheral	(+) Conditions for the
		blood is sufficient)	analysis
	CMPE (BCR-ABL negative)	(+) Differential diagnoses	+
	Suspected AL/AL	+	(+) Not in typical cases
Suspected bone marrow metastases		–	+
	Monoclonal hypergammaglobulinemia	+	+
NHL (exceptions, see below)		+	+
	Typical CLL	+	(+) Prognostic factor
	Follicular lymphoma	(+) To distinguish vs	+
		other NHL
	Hodgkin disease	–	+
Further indications for a bone marrow analysis are:
	Unexplained hypercalcemia	+	+
Inexplicable increase of bone AP		–	+
	Obvious, unexplained abnormalities	–	+
	Hyperparathyroidism	–	+
	Paget disease	–	+
	Osteomalacia	–	+
	Renal osteopathy	–	+
	Gaucher syndrome	–	+

+ Recommended, – not recommended, (+) conditionally recommended, ITP idiopathic thrombocytopenia, OMF/OMS osteomyelofibrosis/osteomyelosclerosis, PV polycythemia vera, ET essential thrombocythemia, CMPD chronic myeloproliferative disorders, AL acute leukemia, NHL non-Hodgkin lymphoma, CLL chronic lymphocytic leukemia, FISH fluorescence in situ hybridization, AP alkaline phosphatase.

28

Normal Cells of the Blood and

Hematopoietic Organs