If the monocyte count is 0, can this result be reviewed?

Monocytes are the largest leukocytes in peripheral blood and are the main component of
phagocytes in peripheral blood.
The reference range of normal adult peripheral blood mononuclear cell count is (0.
1-0.
6)×10⁹/L, generally speaking, monocytopenia has no obvious clinical significance, but can the result of monocyte count of 0 be directly reviewed?

Case history

On July 21, 2022, we received a call from a clinician: "There is a patient in our department who needs to review the blood routine results today
.
”

We looked for the patient's blood routine results, and the results were normal, the instrument graphics were normal, and there was no abnormal alarm information
.
Why does the doctor ask for a review?

We call the clinician to ask about the reason for
the review.
The doctor said: "The patient needs to collect mononuclear cells today for follow-up anti-tumor treatment, and the morning blood routine result monocyte count is 0, will it affect leukapheresis?" ”

Review of medical records: The patient, female, 71 years old, was admitted to the hospital with the
main complaint of "8 years after radiotherapy and chemotherapy for esophageal cancer, eating irregularities for 2 months".
After preliminary screening of pathological sections and HLA typing, patients plan to be enrolled in the "clinical study of novel DC-CTL cells combined with PD1 antibodies in the treatment of advanced solid tumors", and the clinical study requires patients to undergo leukapheresis before enrollment for DC-CTL autologous cell preparation
.

DC-CTL refers to T lymphocytes co-cultured with DC cells, in which T lymphocytes, as reaction cells, activate T lymphocytes through the antigen presentation of DC cells, and generate effector cytotoxic T lymphocytes
.
Cytotoxic T lymphocytes (CTL) are the body's most important effector lymphocytes against tumors, activated by tumor antigens and given anti-tumor specificity
.

Patients collect monocytes to obtain T lymphocytes, not monocytes
.

Why does the monocyte count occur with a 0 count? Our fully automated hematology analyzer has an injection volume of 10 microliters, which is equivalent to scooping a scoop of water in the river, and the sand grains in the water are like cells, the size of the sand grains is not exactly the same, and the volume of different cells is also different
.
The leukocytes in the peripheral blood are mainly neutrophils and lymphocytes, and the proportion of monocytes itself is low, so there will be a situation where the count is 0, but it does not mean that there are no monocytes in the peripheral blood, but there is no
sample injection.

We gave a reasonable explanation to the clinic, and the doctor was very satisfied
.
But our thinking doesn't end
.

Case studies

The proportion of monocytes is 0, can such results be directly reviewed?

The health industry standard of the People's Republic of China "WS/T514-2017 Establishment and Verification of Detection Capacity of Clinical Laboratory Methods" points out that the detection capacity includes a set of performance parameters LoB (blank limit), LoD (detection limit) and LoQ (quantitative limit) evaluated for the detection accuracy near the low detection limit value, in most cases, LoB should be less than LoD, and LoQ can be equal to or higher than LoD, but not less than LoD, and results less than LoD should be reported as "not detected" ^[1]
。

The literature on finding the detection limit of blood routine related parameters found that the minimum detection limit of eosinophils by the Kurt LH750 automatic blood cell analyzer is 100×10 6/L and 10×10⁶/L, respectively, when the number of eosinophils is lower than their minimum detection limit, the instrument reports a result of 0, which must be reviewed manually ^[2].

There has been no literature to report the detection limit of the automatic hematology analyzer we use, and the consulting instrument application engineer has not obtained relevant data, but the instrument engineer recommends that we re-examine the result of the blood count of 0, if the cell is indeed not seen under the microscope, you need to note on the report sheet that the result has been manually microscopic to review
.

Case summary

For biochemical immunity-related quantitative projects, the minimum detection limit of the instrument is very important, and there are few research reports on the minimum detection limit of blood routine related parameters, and in the future work, we need to consider whether it is necessary to formulate the detection limit
of the relevant parameters of the automatic blood cell analyzer.

References:

[1] WS/T514-2017 Establishment and verification of detection ability of clinical test methods.

[2] WANG Fei, LI Qing.
Comparison of automatic hematocytosis and manual counting method for the determination of eosinophils[J].
Modern Journal of Laboratory Medicine, 2013(6):3.